My thoughts, with possible spoilers:
1. I agree with the above comment that the set is a bit over-rated, but it does do some cool tricks, and paired with the lighting, it all works together very well. After Jessica Chastain spinning around a bare stage in A DOLL'S HOUSE and other bare bones examples this season, it's actually pretty spectacular by comparison.
2. Way too many storylines and some of them are resolved in very odd ways. Mateo's resolution is that he bought his mother a gold dress??? Maybe I blinked and missed it because they were rushing everything together at the end, but did Jesse even get a resolution at all?
3. The cleaning lady thing needs a paragraph all on its own. What the actual hell was that? Spoiler, I guess - She comes on for a few minutes in one scene mopping a floor and singing opera to herself. Way later in the show, she makes a second appearance in which she is still mopping the floor and singing opera to herself, but in this instance, two guys in suits are walking by in the background. They stop when they hear her singing and they grab her and rush her off stage. Next, the lights come up on her in a fancy red dress and she is singing opera, presumably onstage at the Met, and then she is never heard from again. WTF?!?!?!?! Stro, seriously, that storyline (if it can be called a storyline) is totally unnecessary and does nothing but add time to an already overlong show. Cutting this entirely would be a very good idea, although I'm sure the actress would understandably be very unhappy about that.
4. There are some very cool dance numbers and sequences in this show. The highlight has to be the tap number up in the scaffolding in the clouds. That stopped the show dead with very long rapturous applause, very well deserved. Nothing else quite lives up to that except maybe the finale when the stage does a very cool trick, but there are some really lovely sequences - the one in the snow, the one in the rain, the Latin infused numbers that have Miranda's fingerprints all over them. All great.
5. They gave Colton two pre-existing Kander & Ebb songs - Marry Me from The Rink, and Quiet Thing from Flora. Marry Me was lovely, but I really hated his rendition of Quiet Thing, which is one of the most beautiful of all the K&E songs. Be sure to look up Marin Mazzie singing it on YouTube if you have not already done so.
6. My biggest problem with the show is that Francine Evans is supposed to be some sort of major, major talent, to the point that she basically (possible spoiler) rockets to fame by the end of the show, although it's not made entirely clear. If the character is supposed to be so incredibly talented, I'm sorry but I'm kind of not quite getting it from Anna's performance. I mean, she's fine - perfectly fine - but her voice didn't blow me away or even come close to blowing me away, so I was like, "how is this woman becoming so famous so easily"? I don't feel like the character would have even made the finals on American Idol if it had existed back then. Again, fine voice, but not spectacular, which I feel like is needed with this particular story arc. I did have the thought that maybe Anna is holding back, or was holding back the night I saw her, as not to do any damage to her voice during previews - because she does have quite a lot of songs, as well as the big finale that had the entire audience on their feet - but I think that had more to do with the great stage trick that was done as the number began.
Anyway, all in all, it's a worthy show and I hope it only tightens more during previews. It could end up being a major hit and even a must see tourist stop, as it truly is a love letter to NYC.