Particularly if you see it a second time, you pick up a cleverness in what Samberg is doing with his weary portrayal of Nyles. This is a man who has learned that nothing has consequences, and (unlike Phil) he mostly doesn't like that (at least by the time we meet him), and he doesn't exploit that fact to be mean; he exploits it to be weird. He can make strange wedding speeches, hook up with whomever he wants, try anything, and none of it matters. So he drifts through the day, again and again, without purpose. It's dangerous to seek metaphors that are too literal, but if you made this a metaphor for how depression feels to some people, you wouldn't be far off. Nobody understands what's happening to you and nobody understands how you feel, nobody except you can see the futility of every day, so you can only sit back and wonder at the foolishness that makes people care about anything.
And of course, into this mess comes Sarah. Milioti is an actress who hasn't had a lot of exactly-right roles in film and television; she can play very sunny and sweet as she did on How I Met Your Mother, but she's a more interesting and emotionally angular actor than that. Here, you really get her as a perfect romantic comedy lead and yet a fresh one. This is a woman who can get past her own shock and bafflement to seek a way to live in the time loop without losing herself, but she also can slice through Nyles' self-pity and his (frankly earned) nihilism. Because it doesn't take long for her to adopt a very different attitude toward this version of confinement than Nyles has. Hers is something more like, we gotta get out of here.
Palm Springs features a terrific supporting turn from the reliable J.K. Simmons as Roy, a man whose part in all this it would be unsporting to explain too much, except to say that the role calls on Simmons' ability to play dry and wise observers of the world, but also his flair for pure comedy. (Nobody but me will likely care that this is a reunion of Simmons and Peter Gallagher, who plays Sarah's father and also co-starred on Broadway in Guys and Dolls when Gallagher was Sky Masterson and Simmons was Benny Southstreet, right? Right, right.) Simmons improves 99% of the projects he appears in, and it turns out a full-length buddy comedy featuring him with Andy Samberg is a feature film I would very much watch in the future.
The thing about a gimmick like time loops is that the thing itself will not sustain interest. We've seen that—Groundhog Day, sure, but also in Edge Of Tomorrow, Happy Death Day and more. It comes down to what you do with it. The good part of Groundhog Day for me has always been the lighter observations about what this kind of life would make possible: amazing people by predicting what was about to happen, mastering a skill through endless practice, and so forth. But the ugly part has always been the way Phil manipulates Rita (Andie MacDowell) intentionally, and the way it all winds up being about his redemption, which solves his problem and gives him everything he wants.
Palm Springs is still a comedy, don't get me wrong. But it's using the time loop idea to think about something interesting. A time loop is a form of meaninglessness, really, and fighting that requires figuring out what you're going to get out of bed for every day. It's not that once Nyles is nice and is redeemed, all his problems are solved. He's mostly pretty nice all along. It's that both of these people have to decide how to add some kind of stakes to their own lives, because if they wanted to, they really could just float in the pool and drink at the wedding forever, and they could even have each other's company along the way.