I myself cannot establish a video chat using empathy with gtalk/hangout users. The text chat works OK. For the video chat, I don't see the webcam image on my gmail contact in empathy, so I cannot make any video call. My gmail contact does see a webcam image in gmail, but if he tries to make a video call, I don't receive anything in empathy. If I use the gtalk plugin in firefox instead of empathy, the video call works without problem.
This is on debian 7. A similar bug has been found on redhat/fedora: https://bugzilla.redhat.com/show_bug.cgi?id=1013822
