This is a good trade for Charlotte; they've been playing .500 ball since the Diaw/Richardson trade, and this trade makes them defensively better, now that they've got a bonafide big to come off the bench and actually play defense. With the muddle that the 6-8 seeds are in the east, the Bobcats still have an outside shot at the playoffs this season.
I feel a little bad for Carroll, since he had just found his niche with the Bobcats before they traded for Richardson last year in the first place, and got pushed way down in the rotation. This season, he's actually regressed to the point that he'd lost his spot to Adam Morrison, so maybe the change will do him some good.