I consider anything 640x480@768k for .wmv's and above as 'high-quality'. That is definitely at the low end of the scale. I typically do our videos 720x540@1024k which I think is more than I usually see on other sites.

We offer RealMedia 480x360@768k which I actually think looks about as good as our 720x540 .wmv's. And they even look good when you resize the window to double-size.