I haven't tested N800 to N800, but others have - it's supposed to work fine. There's even a video showing this, on Thoughtfix' blog IIRC.
But I have tried N800-to-PC, and my experience is similar to yours: The PC party couldn't get the webcam working, although he could see me. The sound was very choppy for both parties, and he reported a 99% CPU usage on the PC app.