Lets get one thing straight. The movie keeps you interested and excited with a well written script. However, I have to admit that subjectively I can neither forget nor forgive the way the movie treats time-travel as a concept. More on this later.
Loopers are the guys that kill people from the future. Simple as that. We as all-seeing viewers and our protagonist, live in the present which is not that different from the 21st century. Some more advanced guns, cars, motorcycles, drugs and telekinetic people able to move a coin are the only differences. In the present, time-travel has not been invented yet.
Here comes the first irritating fact. Some criminal organizations send silver plates and tied-up victims to the past for the loopers to kill them. The loopers just press the trigger, get rid of the body and take a huge amount of money proportional to their job. So, why do they send the victims and a bunch of silver plates to the past with a time machine and not just keep all the silver and burn the victims to a crematorium?
The story of our protagonist as a looper, a realist and drug addict getting his past self into trouble is smart and well executed. However there is one small little problem. This is not how time-travel would work as a whole. Even if we as a viewers are limited by our own nature as persons, the plot of the movie can not be kept the same with critical changes by time-travel. If a person suicides there would be no future self of that person to go back in time in the first place. End of story! This might and could happen in a universe with multiple timelines. Buuut no matter the case, it is established that we watch a single timeline. If his future self was able to come back in time, then there might be some time-scars like changing memories (doubtful) but it is determined that the protagonist would live up to the moment where he was able to time-travel to the past. And the movie oversees such a critical rule.
All the main characters from the past and future protagonist to the single mother and the looper boos, feel their role. Huge respect to that kid incarnating the rainmaker. His expresions and acting talent are exceptional increasing the mystery as well as our curiosity for the future of the rainmaker.
You want to see a casual time-travel movie without a lot of head-scratching? Then sure, watch Looper. The movie has a take-it-or-leave-it attitude defending well the current approach of time-travel. Unfortunately, I left it. Even if the production and acting was exceptionally good, having to ignore such big plot holes was too much for me.
"(Young) Joe: I saw a mom who would die for her son, a man who would kill for his wife, and a boy angry and alone, the bad path laid out in front of him. I saw it, and the path was a circle, round and round. So I changed it."
"Joe: I'm going to France. Abe: You should go to China. Joe: I'm going to France. Abe: I'm from the future. You should go to China."