Normally I'd put full spoilers in my review, because it's hard to discuss a movie while dancing around plot points. But this movie is projecting to be a bit of a box office dud, so I'm going against my better judgment for one simple reason:
You should really go see this movie!
The Good:
Tom Cruise is great. I know a lot of folks don't like him because he's a weirdo, but he really does a great job in this movie. He is very convincing as a smug Major who is pulled from his cushy office/PR job into combat. He conveys a very wide range of emotions in the whirlwind couple of days leading up to his first attack on the beach.
While it's no secret that the movie is like Groundhog's Day, it bears almost no resemblence to it. There is a real reason Cruise is repeating the day - and it's not to find true love with Emily Blunt. (Although who could blame him if that happened along the way.) While Cruise's day start the same way, the way he wakes up is slightly different. He must have filmed himself waking with a jolt hundreds of times, and his reaction is very well matched to the way the previous day ended.
They never say how many times Cruise lives his day, but it must literally be in the hundreds or even thousands. By the end of the movie, even though he hasn't aged a day, he looks tired, worn out, and battle hardened. The smug look and fear from his early days completely gone.
The movie is surprisingly funny, but at the same time builds the tension to a level higher than most movies of this type. While you always feel like Tom Cruise will find a way to save the day, the fact that he can die and reset means you never really settle in to a feeling of "This is the time he makes it through this part."
The writing is great. The plot could have easily been muddied and confusing, but they explained everything perfectly. While it's of course a ridiculous concept, time is taken to let people get used to it before they start building the story.
The Bad:
The only minor nitpick is they never really explain why they're sending Cruise into combat in the first place. It seems sort of random. That may have been what they intended, but there seemed to be some malice behind it on the part of the person who sent him, and an explanation for that malice would have been nice.
The Ugly:
Well, there is one other thing. I'll dance around this as much as I can, but the ending....Look, it's a satisfying ending, but for some people I think it's going to detract from their enjoyment of the film. And I'm not 100% sure it makes sense. Only a rewatch or two will help me reconcile it with the rest of the movie.
I think most people will be fine with the ending, so I'll give this my strongest possible recommendation. The critics didn't quite have it right - It was not almost as good as The Winter Soldier and Days of Future Past - in my opinion, it was a little bit better. I think the main reason is it was about 20 minutes shorter, so the pacing was just a bit better. Also, most of the film is centered on Cruise and Blunt, which made it feel more focused.
So with no disrespect to TWS or DOFP, I'm calling this the best movie I've seen this year. In fact, it's the best movie I've seen in two years.