I have an ATi TV-Wonder and it's awesome.
It has some seriously painful Win2000 drivers, but in Win98SE it rocks
If you plan to use Win2000 then stay away from it, but you said Win98 so I highly recommend it.
Edit: Actually I've heard that the newest beta drivers for the TV-Wonder in Win2000 work pretty well for everything except video capture. But I've never personally tried them.