Now that Sonar has Melodyne and I bought the upgrade, I use V Vocal.
I suppose that's because I used Sonar Xi Power Books to help me understand V V and experiment with it. But, there's also something about the Melodyne interface...I just don't like it yet, but I haven't really given it a chance either. I know it's powerful.
I use V V to adjust my vocal pitch as necessary, don't tell, and I use the Dynamics module to smooth out my vocal takes where I was either too loud or too quiet, too much or not enough consonant on a lyric, adjust sibilance, etc.
I love V V for what I need to do with it, and it works fine for me.