Now I've watched the whole thing and read the commentary, so what follows will obviously contain spoilers.
The first thing to say, I think, is that the reboot completely fails as a story taking place 10 years after the original ending. They should have just picked up the story two or three years on, disregarding the chronological disparity involved and covering up the physical aging of the actors with makeup. (Not that hard, really, considering that all three of the female leads could nearly pass for their original ages still.) If, as a viewer, you will yourself to think of the reboot as taking place in 2009 or 2010, almost everything will seem a lot more reasonable - Rory's affair with Logan, her professional floundering, the Luke/Lorelai relationship impasse and its resolution, etc. If it's true that the writers intended all these outcomes in the original series, then it follows that they'd only make sense in 2010.
So let's imagine that this show depicts the Gilmore Girls circa 2010. Lorelai and Luke have been back together for three years but, given their checkered marriage histories, are not sure whether to finalize the deal. Rory used her one-year campaign blogging gig to get a foot in the door and freelance in a few impressive venues over the past two years and is now unsure which direction to go for a permanent job - staff writer? professional freelancer with royalty income from books? lower-level editor with freelancing on the side? These are legitimate questions a 25 year-old journalist could be anxious over without being a washout. Characteristically weak-willed Logan was unable to stick to his demand for marriage or nothing on graduation day, and she in turn was indecisive enough to accept his invitation to continue their relationship under the radar. Richard has just died. See how that all seems so much more plausible?
In this context, the main question that the reboot sets up to answer is, now that we have all grown up and more or less attained our youthful goals (the attainment of which was the subject of the original show: Rory getting into Harvard-then-Yale and becoming a writer, Lorelai opening her inn, the multi-generational Gilmore family re-establishing a loving, if fraught, relationship), how do we remain satisfied in the lives we worked so hard to create? How do we settle? Not for something, which implies lowering our expectations, but how do we settle into expectations we've met? Because once you've got what you thought you wanted, there is always the threat of discontent, the danger of restlessness and underutilized ambition, which always wants growth and expansion, new things and more of them, and is never satisfied with the attainment of anything, no matter how intensely it was longed for before it was attained. Let's call this problem the Adulthood Question.
The Adulthood Question is a big part of Lorelai's plot arc in the reboot. She's made the Dragonfly into exactly what she imagined, but Michel urges her to expand, and she begins to question her own satisfaction. (And in the background, Sookie has left out of an inability to accept that what she had was in fact what she really wanted, although we have to assume that was more the result of McCarthy's schedule than the writers' wishes.) Lorelai's finally got The Guy, but doesn't know whether that's all there is to it; by getting The Guy, you get a nice, reliable "roommate," as Emily calls him. Emily's widowhood is a down-the-road restatement of the Adulthood Question - how do we live when the passage of time takes away the life we've settled into and learned to love? Even Rory, though she hasn't yet decisively established herself, has already largely become the person we saw her aiming at in the original show, and now has to decide only what version of her goal to select, though she has yet to address the family question.
If you continue to indulge my re-imagining of the reboot as taking place in 2010, then Rory's unplanned pregnancy is a very fitting resolution to her problems. As I wrote of the original series, this is a show that celebrates motherhood and emphatically argues that unplanned pregnancies do not have to ruin your life. In the Gilmore Girls, unplanned pregnancies jump-start adulthood for all of the women who seem like they might never reach it without a major intervention.
This LA Review of Books review (via Will Baude, whose post has a good round-up of other reviews too) is interesting, but I think ultimately wrong to see unplanned pregnancy as a mark of failure or unmet expectations in the show. That's only how Richard and Emily viewed Lorelai's pregnancy, but one of the main points of the original series is that they were quite bad parents to Lorelai - not as bad as Lorelai made them out to be, but certainly far too uncompromising and concerned with appearances. But pre-pregnancy Lorelai was hardly a diligent little bookworm on the road to Phi Beta Kappa at Yale like Rory. Teen pregnancy turned out to be a way out of a life she hated and into one for which she was suited. The other unplanned pregnancies in the show (Sookie's, Lane's, Christopher's wife's) are much better-received than Lorelai's.
And Rory's pregnancy at 25 (I insist!) occurs in a very different context than her mother's. Precisely because she gets along so well with her family, she isn't going to be raising a child on her own while scraping by as a hotel maid, but will have her mother and stepfather, grandmother, and we must assume the entire town of Stars Hollow, which still worships her, to help. Not only does her pregnancy not foreclose her writing career, but we're given reason to think it will focus and advance it. Given the timing, it's the pregnancy that finally motivates her to get serious and write her (probably slanderous, self-absorbed, Millenial stereotype-reinforcing) memoir. The fact that this pregnancy is not preceded by marriage like Lane's and Sookie's pregnancies were might give us pause, because what does it mean that you need a baby but not a husband in order to finally become an adult? But Rory is also her mother's daughter, and her independence from/inability to commit to men is an important continuity. (There is also the suggestion that Rory's future Luke will be Luke's own nephew, Jess - more continuity.)
So I disagree with Will and the LARB that the reboot is, or at least is supposed to be, dark. I don't think the point is that everyone will immediately celebrate Rory's pregnancy as though it were the most desirable event in the world, but the history of unplanned pregnancies in the show should give us good reason to believe that the characters will eventually be grateful for it. The Adulthood Question only has one broadly accessible answer, and that is children.** Children channel restlessness and underutilized ambition so that it doesn't leak out of you and ruin your life by making you perennially dissatisfied with everything you've worked for and always on the hunt for more and better. Children give you the novelty and open-endedness you desire, but in the form of someone else - a new person you bring into being, one whose future is still open, and who must be guided towards it by you. You have to stop worrying about your own ascent (is it high enough? is this as good as it gets? should we add a spa to the Dragonfly?) to launch theirs. So Rory's pregnancy actually solves apparently unresolved problems in the show by giving both Lorelai and Rory a new outlet for their ambitions (since apparently Lorelai won't have more kids of her own) while also helping to satisfy and anchor them in the lives they already live.
The Adulthood Question was actually set up in the original series by the problem of the Small Town Where Nothing Happens and Everyone Is Average. How can an intelligent, ambitious person be content in such a place? Most of the original show allowed us to assume that the children raised there were really destined for greater things: rock stardom (Lane), beat-revival poetry (Jess), Pulitzer prizes (Rory, obvs). But that assumption doesn't really work in the long run, or small towns would be unsustainable and everyone has only the choice between being a star elsewhere or a failure back home. There has to be some positive appeal of such a place, some reason to end up there instead of just beginning there and then moving on to greater things. I think the reboot does try to show that flipside by showing that no place can be big enough and exciting enough for the internally dissatisfied person who hasn't answered the Adulthood Question, while for the person who has, Stars Hollow's virtues will be clear.
The other triumph of the reboot was Emily, who solves her problems on her own, with only the help of her maid, while keeping a stiff upper lip and revealing vulnerability only rarely, and then only to her immediate family. Someone on the writing staff must be a great fan of midcentury WASPs.
All that said, significant problems remain. It was too much the parade of cameos, with most of the significant secondary characters from the original run appearing only in one episode and often only in one scene, giving us a quick update on what they've been up to, and then immediately disappearing again into the ether. The result is subplots of weirdly time-consuming but then eventually one-off things like the town musical, and a lot of loose ends. Does Paris go through with her divorce? Does Sookie realize what she's missing and return? Also, Rory's brilliant career idea to write a memoir is pretty lame. I completely support Lorelai's objections to it. A final important question: why didn't they use the old theme song until the closing credits? I loved that theme song as an opening. A definite minus in the reboot.
* "Farm your own field, don't try to farm the fields of others" is my husband's summary of the moral of Herodotus' History, which he repeats to me when I suggest undertaking some massive project completely outside my wheelhouse instead of focusing on all the projects within it that presently remain half-done. In Herodotus, this point is made by Cyrus in the final paragraph, when the Persians suggest to him, "Let us move from this land of ours - for it is little and rocky, too - and take something better than it. There are many lands next to us and many further off, and if we take one of these we shall be more admired for more things." But he tells them that their pursuit of something ever-better than what they have (which is what has already made them great at this point) will only result in their conquest by others.
** Another answer is the kind of superstar career where you go from one important and all-consuming project to the next, and so always have a newer and bigger thing on the horizon. But that kind of life is not open to most or even many people, including most Yale graduates, however enthusiastically they might believe otherwise while they're at Yale.