I find reatune in manual mode extremely transparent and efficient for minor correction. I never needed more than that, honestly.
I would leave it at 250ms in the pro mode do keep it as transparent as possible.
Yeah, for someone who can't sing at all, it's not the plugin for you.. but then again, if you can't sing at all, why don't you try to improve your singing instead of trying to fix it when it's beyond repair? No matter how hard you try, a heavily edited voice will always sound... well... heavily edited.
My motto is, if reatune can't fix it, you don't need a better VST. You need a better singer.
Here is a nice little tune I did recently...
http://www.kompoz.com/music/player/5...1?isPopup=true
Let's play a game: try to find where used reatune.
IMHO, reatune is one of the most transparent tools out there, aside maybe for melodyne.... but melodyne is pretty expensive, and has a pretty steep learning curve.