On my 1.5Ghz 17" Powerbook, I quit every app, including the finder, (and closed all my widgets) except for VirtualPC.
I then ran Ventrillo.
Result: I could hear them (with slight distortion toward the end of their comments. It got worse, the more apps I had open. Which was why I closed them all.). But I could not speak. When I got the microphone, I could speak, but not hear.
Fortunately I have a crappy pc laptop from which I can hear but not speak. So I listened to the performance of myself speaking in vent on the mac, and it was choppy as HELL. I mean wow. 100% of the computer's resources were being piped to VPC / Ventrillo, and yet I could barely make out a word of what I was saying.
Pretty lame.
- Xidius