Just got the card, and a lot of tweaking needed! I've been fiddling with this quite a bit, and the card and the TV seem to be fighting each other every step of the way. The good news though, is that the image looks fantastic! Probably the best that I can expect from this TV.
This is what I have so far:
720p dip switch on dongle (720p looked better than 1080i and 480p was huge!) Note: I didn't want to mess with the service menu, because I already adjusted the TV for the PS3 (had major overscan at the top) and I'm very happy with the way it displays PS3 games. As a result, their is some underscan at the top of the screen with the PC, but I'm cool with it. It is worth the trade off.
Desktop initially set to 1024 x 768
Used Catalyst to adjust the resolution so that everything fit on the screen. The result is a strange resolution (1184 x 676) but it fits nicely!
Mame set to D3D, 1024 x 768, 32 bit color ***strange problem though: I'm running three different older versions of Mame because I have roms that work on one version, and not the other. I sure wish I could fix all of my roms so that they ran on just one of them! I've heard about clrmame, but it seems confusing. Anyhow, the two oldest versions work great, but the newest version that I have, .116, squishes all of the games to the center of the screen! I had to turn off enforce aspect ratio, and enable the GameEx vertical bezel in order for the games to fill the screen. The GameEx bezel actually prevents the vertical games from being stretched across the screen, since enforce aspect ratio had to be set to off. The horizontal games looked fine, and filled the screen. I wish I knew why the older Mame's work fine without having to do this!
Fusion, Nestopia, ZSNES, set to 640 x 480 (otherwise, for some reason they wouldn't fit the screen right)
Project 64 set to 1184 x676. Although this still puts the image in a letterbox, the bump in resolution looks great compared to 640 x 480.
Unfortunately, Hamsterball has to be run at 640 x 480, otherwise at 1024 x 768, it just runs in a smaller box in the center of the screen.
Overall everything looks great other than some of the weird issues noted above. Most of the games look the best I have seen them outside of the arcade. Specifically, classics like Robotron, Donkey Kong, Dig Dug, Galaga, etc. Or, newer Capcom fighters like Street Fighter 2. Some games like The Simpsons, The Legend of Kage, and Teenage mutant Ninja Turtles look a little bit blocky. Although, I seem to remember That The Simpsons looked a little blocky in the arcade...
Anyhow, if anyone wants more info, or has any tips based upon the above, let me know!