I saw Looper on Saturday but my feelings on the movie are still fresh. I've already recommended it to a few friends (the few that haven't already seen it, that is) and I think that's about the right approach to it. It's a movie you tell your friends to see. You caution them that it's not Primer and they shouldn't spend too much time puzzling through all of the Timey Wimey permutations of the plot. You tell them it isn't worth it.
Don't get me wrong, Looper's a lot of fun. The world depicted in the movie is low-rent but believable. The world of 2044 isn't so different from our own: slumping into decay; grimy cars retrofitted for natural gas and solar panels, cities awash in corruption and glittering sky-scrapers. The difference is that the world of Looper is in contact with another future, about 30 year later that keeps sending the people it can't properly kill to be assassinated and disposed of in the more unruly past. The Loopers of the title are contract hit men, paid to kill the people that drop in, bound and hooded from the future. Eventually, every Looper will need to 'close the loop,' in other words kill their future self which future criminals eventually send back to tie up all of the loose ends.
Of course loose ends are what make movies interesting. So it's not much of a spoiler to reveal that Joe Simmons, played by Joseph Gordon-Levitt, is put into an impossible situation when his future self (Bruce Willis) out-foxes him and escapes.
The key moment of the movie, for me, takes place at the end of the first reel when future self finally confronts his past self face-to-face. Gordon-Levitt does a great impression of Willis' grave, furrowed-brow approach to acting. Willis looks into the eyes of his young self and performs a very nifty bit of wish-fulfillment by taking the head of his younger self and slamming it into a diner table. Who hasn't had at least few moments of outrage about the sabotage of past selves.
There's more to the movie than that but for me the principle reasons to see the movie are all in the first hour or so. Weirdly the movie starts big and seems to shrink over time and until we're left with four people in a corn-field. There's an ending and it's best not to dwell on it too much.
See the movie just don't pretend it's something it's not.