Lovin' the IV!! True-tone-snobs say that only V I sounds 'awesome', but I remember tryin 'em out in the music store, and let's just say that the pitch-shift sound wasn't exactly Eventide/Lexicon quality..
And I usually run mine w/distortion to disguise the artificial tone. Remember, too, that the Whammy's not an 'intellegent' harmonizer, so unless you really work things out in advance, you're gonna hit a few clams in any given scale.
But I mainly stick to the octave up/down mode. Like Jack White, I'll loop a riff 1 octave down & play over what sounds sorta like a bass part. That same preset's good for adding hi-pitched squeals to the end of a lick, a la Joe Satriani.
All in all, a fun box, but best used in an effects loop, as the buffer's real *tone-sucker*.