I just got my Gainward gf4 ti4200 VIVO and have messed around with the video in a little. I tested it in windows 98se and windows XP with very similar results. I was capturing video from my HI-8 camcorder via s-video cable, I have not tried anything else yet, but plan to and post some more detailed experiences becuase I know alot of people have questions about this, myself included. I learned some interesting things in my short time using it. First of all, I don't know how much the software your using has to do with your results, but for what it's worth, I was using the Intervideo WinCoder program that came with the card on a 17 inch Sony trinitron monitor running at 1024 x 768.
Once I adjusted the color settings, the video looked great. I must say that it looks much better on my computer than when I hook up my camcorder to my TV. It is crisp, clear, and flawless. BUT the resolution that looks so good is ONLY 320 x 240!!! That is about a 3 inch square box on your screen. 640 x 480 looks ok, but is degraded a little and grainy. It too is a pretty small box this time about 5 x 5 inches square. If you play the input in full screen mode, it looks just horrible. Big giant grains, blotches, and color distortion, nothing worth recording for the intent to play back at full screen. If your only plans are to play clips in a smaller box, this is just perfect and has great quality.
I know that is a breif overview and to the point. I only had a couple hours time to try it out. I am sure there are probably more settings and adjustments to get more out of it, but I haven't got to them yet. So this is more of a what to expect out of the box with no experience kind of thing.