I was playing with iChat tonight and discovered a bug with the video chat.
In the image above I'm using Apple's video test users to simulate a four person video conference. You'll probably notice that the leftmost video is the only one that is displayed clearly. The others appear severely degraded. When starting the video chat, the video is clear. When the user on the right is added the first participant's video becomes degraded. When the final user is added the second participant's video also becomes degraded.
Bandwidth limits and latency being what they are, I expect some degredation, but it's really lame that the first two users suffer while the last one looks perfect.