All in all it was pretty awesome. It was, as expected, Groundhog Day combined with an alien invasion. That might seem like an odd combination but they did a pretty good job of it.
I've only got two significant complaints about the movie. Number one is that i think the ending was a little too predictable and wrapped things up a little too nicely. (And arguably did so via a minor "cheat".)
Number two is that it starred Tom Cruise. He did a perfectly fine job acting, but i feel bad about giving money and recognition to Scientology. Even at the 2nd or 3rd degree.
(And because apparently there are still a few people out there who don't know that Scientology is seriously bad juju, here's why: http://en.wikipedia.org/wiki/Scientology_controversies "Operation Snow White" and "Operation Freakout" are probably the best known issues.)
Also, on a side note: It's set up right at the beginning that the alien pod crashed in the middle of Germany. You then see a map of the aliens spreading through Europe, colored in red of course, until they've got pretty much everything. And now the Allies (technically the United World something or other i believe, but the UK and US are the primary featured members) are staging an attack out of Britain onto the beaches of Normandy. So it's definitely a blatant WW2 allegory, with the Germans cast as an alien hive mind. I wonder how well the movie is playing in Germany? =P