I just had a Qik chat with my fiance and the video of him was very pixelated and choppy, but I could still tell it was him. The only problem was that I had to push the talk button for him to hear me (he initiated the chat). I don't know if it's user error or what.
Overall, I would have to say that it's a pretty cool feature regardless.
I did a test Fring call to a buddy with an iPhone. It worked just fine. We were both on wifi but seemed to only get about 5 Frames per second. The audio was just fine though.