I did research and read the forum threads on which pitch correction to use before I laid my hard earned dollars down.
I wanted a straight ahead no artifacts fix for a vocal and make it sound good, and natural.
The one I settled on was Melodyne. I bought it as Melodyne Plug In... they sent me a few upgrades and I ended up with Melodyne Editor on the last upgrade.
It's transparent and everything I could want in a pitch correction package. I don't often work on a vocal track that doesn't get the melodyne treatment..... especially the lead vocals no matter how good they sound before it.....they always sound better after. Note: I do occasionally let a BGV slide by without fixing it. It adds ambiance to let some vox tracks be slightly out of tune.
Editor does melodic solo stuff like voice and sax as well as the poly stuff like piano and guitar.
Just yesterday, I was working on a dobro part where the player (live player) was flat on a few notes and on one slide up was also a bit flat. I grabbed the audio in a 3 measure clip and let Editor display it as poly. I identified the flat notes, including the one with the slide...and corrected it perfectly as if it was played correctly from the start.
In my humble opinion....Editor is worth every dollar it costs.