I ended up guessing about half of what was going on because my immediate initial thought was "You don't wipe someone's memory if everything is on the up and up". I very quickly realized that the "scavs" were actually the real humans, and that Cruise's character was working for "the aliens". Of course, I didn't realize that there weren't aliens, per se, but rather, an alien machine, and I didn't realize he was a clone (though I knew that the "radiation zones" had to be some huge lie).

It was extremely enjoyable, however, and even threw in a few lightweight philosophical questions about identity, memory, etc. the way that sci-fi often does.