Pneumatics are neat....but I think they're a real pain. Don't get me wrong, we used them in our 2003 robot, and that went to the Finals on Einstein..so it was by no means an unsuccessful design..but for the most part, I think it's caused more grief than it's worth. Leaks, breakages, etc..are a pain, GR.
As FIRSTers say, Keep it short and simple
. Pneumatics tend to get on the more complicated side..if there's an easier / more efficient / (any other way) to do something, I'd go that way.