Saw this tonight. Tom Cruise is in his usual form as Jack Harper, a drone repair guy in post-apocalypse earth. Apparently, the entire population was moved to Titan (moon of Saturn) and the only humans left on earth maintain the automated drones that stamp out the remaining Scavs (aliens of some sort). Earth, however, is mainly ruined, reduced to a source of water for hydrogen fusion reactors...it's running dry. He lives in isolation with a lover, had his memory wiped before the assignment and is about to be rotated out.
That's all pretty much established in the first 10 minutes, so the main plot is about how things are not what they seem to be. Harper has traces of memory of a previous life, having been married to a woman who manages to show up on the planet. He also maintains a rural hideaway in a small green part of the planet, AND...he finds a bunch of humans still living in a subterranean hideaway, let by a hundred something Morgan Freeman.
How does this all fit together? Is there any hope for humans? What IS Jack remembering? It's all somewhat cleared up at the end, although this is not an easy movie and there are a lot of nuances that may need a second viewing to clear up. The movie is visually terrific, with an engagingly believable barren earth and scary quick glimpses of aliens. Tom Cruise is no better or worse than he usually is. There are hints of Phil Di*k, Top Gun and a lot of other movies. It's not exactly derivative, but it does draw on lots of sic-fi conventions. I was not bowled over, but I have seen worse sic-fl flicks. I don't know that the plot justifies the seemingly enormous amount of money spent on production, but I enjoyed it.