The version 4 update really seems incredibly impressive, to the point of "how did that guy invent this?"  Amazing software, for sure.  These new upgrade prices are insane WHEN compared to just buying outright as well.  Needless to say, my GAS is really being tested to the limit.  But after thinking, I really don't use Melodyne that much.  I've had "fun" with it, bought Editor upgrade last year, but really haven't delved into the polyphonic stuff either.  So with it sitting in my computer for a year, I'd really haven't used it.

I record a lot of VSTi, and I also don't feel the need to really tweak my guitar tracks.  Although I know you can get creative.  Vocal recording is minimal, so that's probably why I don't use it that much.
 
So one question... who uses it...and is it for "creative" purposes or for "correctional" reasons?...(or both :-)  )

And who will ADMIT to using it?
 
I read an article recently where Alanis Morissette was quoted as saying that she asked her producer once about the prevalence of auto-correcting vocals.  Apparently only she and one other singer WEREN'T using it, although some had their vocals corrected without the artist's knowledge.

I have never used ANY pitch correction software of ANY kind! The people that I work with are all old school talented vocalists that pride themselves on NOT having to use Auto-tune or any other device to cover bad vocalists. I am very fortunate in that aspect. There is a joke sign on the wall of my project room that says "If You Can't Sing, Please Don't Sing!"

Sidroe
I have never used ANY pitch correction software of ANY kind!

Have a cigar 

I'm not dismissing the creative uses either. Some videos really caught my eye using it

I find it indispensable. However, I can't remember the last time I used it on a lead vocal line?... I use it on backup vocals to create better (more interesting?) harmonies. But I also use it on metal guitar solos. When you play an almost perfect take but there is just one or two flubbed or overly dim notes? Fixing it in a snap, without having to attempt to punch-in during a finger pretzeling note blitz, is a guuuuuurdsend!
 
But my main use for Melodyne has always been sound design! With the Editor version's polyphonic capabilities, it is a playground for sound mangling! How quickly you can slice, shrink, extend, morph and change bits n' pieces, is the programs true strong suit! Which is pretty amazing considering what it was originally intended for?
 
I just purchase the upgrade to Studio and after looking at the videos, I'm not afraid to admit that I needed a wipe down...

I forgot to mention, if you're struggling to get the right feel when programming drums and your controller or midi device isn't getting tapped out parts down the way you want? Beat boxing the bits in Melodyne and then converting them to midi to trigger your drum sampler, is a handy and quick way to achieve loose feel drum lines!

I will stand up and be counted.  It can do amazing things for bu vocals and a lead vocal, bass or guitar clam.
 
Rocky

I use it often to create richer/fuller background harmonies. I have vocalists sing two or three parts, then use Melodyne to create four or five parts, duplicating, raising and lowering the original three. It can sound like I have a dozen or so in the choir.
 

Fixing bad notes in live performance recordings.
"Tidying" multi-part harmonies.