Really good
SPOILERS
I enjoyed this a lot. The heist plan was great, and was really well executed. I just have a problem with the ending. It came out of left field, as to Donnie being the mastermind.
They gave us a hint as to the garbage truck drivers, doing something according to another plan, but that's really it. We never got an indication that Donnie was really the smart one.
Another problem is Big Nick with his family issues, and that being unresolved. Maybe that is being saved for the sequel later this year.
Other than that, it's a really good film, and quite enjoyable.