I have Melodyne Editor 1.2.1 which I have used as a stand alone but am not a pro with it by any means.
It works very well but sometimes is difficult to avoid a Phase shift sound when moving things too far.
This is probably due to my inexperience with the program and may be totally avoidable.

It can also be used as a separate window plug-in in some DAWS and requires drop and drag I believe.
Have never used it that way however.

The newest version is 2.0 and features Rewire compatibility which lets you open up to 4 separate tracks in the stand alone version of Melodyne and when you click on them they appear on 4 separate tracks in your Daw for real time manipulation.
That seems very cool.

Checked with PG and BIAB/RB currently does not support Rewire.
A good one for the wishlist.

Even so I will probably upgrade soon, as there are a few new time adjustment features which may help me (and I'm a sucker for an upgrade, just ask PG!)
But bottom line on vocals is just keep working at it, you'll surprise yourself.

Carkins