...Actually this Reaper shifter is pretty good. It has a lot more parameters than Logic's two (pitch and formant). And you can adjust by cents. I suppose it does help my droll voice. It seems like +125 cents is about the limit when it comes to keeping it natural.
Would still like to hear from anyone that uses Melodyne, or any other plugin--or even hardware--that does formant manipulation. I think on South Park they record speed up the recording, which is much easier to keep natural.