Related to this, I just watched Fab's tutorial on Melodyne on Puremix.net and it's the best one I've seen yet (going to watch the video in this thread next). Fab actually teaches you about editing vocals, and discusses things like the need to fix the vocal in context and not in isolation, and how you do NOT want to use pitch snap (and why). I found it interesting how he said that a vocalist will often be just a bit sharp when going down (especially in large intervals), and often a bit flat when going up. Knowing that, you can tweek notes not to be in perfect pitch, but to sound like they would have sounded if the signer had sung them properly... cool stuff.