Sound issues with Melodyne?

I have Melodyne Studio so this issue might not be present in the (Essential) version that comes with Sonar, but I've been noticing an artificial sound in the vocals after applying it to a vocal track.  Even if I'm just moving the pitch a few semitones. 
And I've noticed the problem has gotten worse since they released the latest update, 4.1.
If I change the pitch in a note, it'll often sound unnatural or just sounds like the quality isn't as good as the original.  And again, this is for notes that I just changed slightly, like a C to D#.   
I have Melodyne set for the WAV format at a sample rate of 48000 khz and I haven't changed any of the harmonics or tonal settings.
Anyone else noticing this decrease in quality?  Any suggestions of what I can try?
Thanks!