Canobie Paintball, Windam NH - I only played a big game which could have been better.
Boston Paintball, somerville, MA - They freakin' rule as far as indoor goes. The hamster wheel gets tiring though, you'll get bored at the four hour mark.
Forget any nasty stuff you hear below about the field. It's under new managment, Paul the new proprietor is one of the coolest guys I've ever met. He genuinely loves the game and running the fields, and wants AG paintball to be king of New England like it was in the early 1990's. I've talked at length to him about what he plans to do to the field, he's gonna add a little variety by adding a speedball court or two, and he's gonna rearrange some of the fields that currently exist to add balance. As it is now, the field is awesome again. The staff is friendly, they run games quickly, they even allow for side-switching if the games are over fast enough. They've rearranged the barn so it's easier to get your paint and your air fills, they added outdoor nitro fillstations that are self serve (bye bye long airlines for 3k and cooked tanks) Paint and admission prices have gone way down, and they even periodically offer BYOP days now.