I always cut my pork butts into pieces, sometimes as small as 2.5 pounds. I do this because you end up with more of the best parts - more bark, more smoke ring, more smoke flavor. I think Paul's concern about the meat suffering from being cooked too fast can be avoided by making sure your temperatures in the cooker stay around 225. In fact, it still usually takes at least 10 hours, often more like 14, for the meat to be done, so I don't think I'm losing the benefits of low-and-slow cooking. Bottom line, though, is that I get a lot more bark, and I'm happier with the end result.