I've used the Antares model pitch corrector (don't know if it is the same one) and it was kind of a mixed reaction thing. At times, you could really hear it working, almost like speeding up and slowing down of a tape (and this on a digital system). That sucked.
What I really liked it for was those late night sessions where you have complete vocal fatigue from singing all day, and your ears are shot from listening all day. It really seemed to do well if you aren't TOO far off of the note. I plan on putting the ATR-1, the rackmountable, real-time pitch corrector in my rack when I fall into an extra 500 bones, but it won't make a decent or bad singer gold. You have to go to Nashville for that. Just listen to a live boy band...
Pete