1) the acting (Willis' acting was up to standard, but the rest: jesus christ...)
2) they didn't pursue the more interesting questions enough, and thus there were too many holes in the plot (particularly in connection to the "rain maker"; there's just so much left unexplained)
4) Jeff Daniels playing evil
5) with a great theme like this, there's just no reason why 1 hour of the movie should take place on a farm (the most exciting thing that happens is the kid shouting a hole in a visiting Looper)
I'm sure I could go on....
Overall, just an unimaginative script, not impressed with the screenplay nor the acting. I'm a huge fan of this theme, and I just thought everything about this movie was a huge letdown. Maybe my hopes for it were too high.