A strong, but flawed, SF actioner.

Rating: 7/10 (19 March 2013)

There are a few of the persistent criticisms of Looper that genuinely stick.
The biggest of them is that the plot device of the 'looper' is arm-wavy in the extreme, and doesn't stand up to close scrutiny; a lot of whether you can like or not like the film will depend on whether it falls for you at that hurdle or not. It's basically never entirely clear why it's so difficult to dispose of future bodies that time-travel is a preferable alternative (along with a host of other things, like "why send them back alive?" and "how is it that only the mob has this technology?" and "why have 'loopers' close their own loops?"), so you have to either decide to suspend disbelief for that or not.
It has also been pointed out that (this is a SPOILER) having Old Joe kill a toddler on his Terminator-esque mission to assassinate an evil criminal mastermind called the Rainmaker (whose men accidentally murder his future wife in the course of trying to 'close his loop') is rather cheap upping of the ante; I think it is valid, if horrific -- and the horrific nature of it underscores that Old Joe (Bruce Willis) is *not* on a heroic mission -- but that it could have been handled better and less manipulatively.
Lastly, it's been pointed out that the women in Looper suffer from Frank Miller Syndrome: they're almost all some variant of prostitute or junkie (current or former) with weird issues around motherhood. That isn't good and it gets distracting once one notices it.
The other common gripes about the movie look to me like cases of viewer inattention than flaws in the film itself. The time travel mechanics are straightforward and make perfect sense, the filmmakers make a good decision in having the characters *not* spend the whole movie explaining time travel to one another (much less the politics and socioeconomics of the setting -- no thank you, two-hour features are not a good venue for that). The action is appropriate and for the most part refreshingly restrained, and the one scene that isn't restrained is illustrating a specific point (about the relative back-woodness of Young Joe's Kansas mob operation that's been repeated throughout).
Some people complain about suspending disbelief for telekinesis, but it's no more or less science-fantasy territory at this point than time travel is; others complain that there were "two movies," one about time travel and one about TK, but that is false (TK is the Chekov's gun of the setting, mentioned earlier on and primed to go off by the third act, and is a good shorthand for the expansion of human potential). The cinematography is stunning, the performances (barring a few false notes from Emily Blunt) are excellent -- especially Gordon-Leavitt's Young Bruce Willis homage, which manages not to be an impersonation -- the story is involving, and on the whole I recommend it.