Sarah,
The key to using the VO tool is a good mike (as in any situation); and a proper setting. I have used this with good success; however I found it impossible to do on my main editing suite, which runs a G5 with 1,000 internal fans (go intel). As a solution, I do this in another area using my MacBook Pro laptop. The results have been as good as the room I am in.
Good luck
Al Davis
Visual Velocity
Brookline, MA