I just tested this myself by getting called by the girlfriend. She used the "video call" feature from the chat inside Gmail. It worked for a few seconds until I started my camera on the n900, then it disconnected after receiving a few frames from me. I was able to receive video from her all this time, though in very poor quality (missing codecs maybe?).

However, this is a good sign! I hope we'll get something out of it with a few patches.

EDIT: After playing with this new feature, my CPU went crazy (load average of 10) and the OS started swapping until it ran out of memory.

This is the process that's raping my device:

By the time I'm finishing writing this post, the device has stopped responding. So be careful when you test video conference, you might lose some data if were working on something in the same time.