I agree with this comparison. I would probably not use QuickTime to encode anything streaming - However, for high-bitrate video clips, I find QuickTime is very acceptable.
I'm a little split on DivX, however. I like the codec, but I couldn't playback anything on my old Windows box. It would blue-screen about 5 minutes into any DivX encoded clip, which leaves me to believe that DivX doesn't work with some video cards/system configurations.. So far, on my iBook, it's been good. But I don't know if I would rely on DivX.
Windows Media? Ha. I didn't even know that there was no Mac encoder available. I wouldn't even use it if there was one.