I'm using the onboard video on my VIA EPIA M-10000 motherboard and standard DOS MAME with mixed results.
I'm using VGA cable->WG arcade monitor, not using the TV output.
I've only tried a few dozen games so far, all of them classics. Galaga, pacmans, frogger, all work perfectly. Donkey Kong, DKjr, and several others show up 1/2 off the screen and are in a really small screen size. Obviously, my video system can't handle the mode these games require.
I'm currently trying to tweak advancemame to support these modes, but it's complaining that it can't load a video driver for my video card. I think it's just a matter of forcing it to accept the ID of my video card before I can at least attempt to set up good modes for it. This requires recompiling advancemame though. (I think. I'm doing research on this right now.)
If it can work, these VIA boards are really quite perfect for an oldskool arcade cabinet. Small size, low power, cheap, easily has the horsepower for classic games, and it's got everything you need onboard. I hope it's just a matter of a few software upgrades to make it fly.
-jeff!