I'm running Mame CE3 on a Compaq iPaq 3635, and several of the games, while they do run, are oddly formatted and don't fit properly on the screen.
For instance, Sidearms: the right side of the screen is about the middle of the game screen. For R-type II, the ROM warning screen is huge and flickery, then when I hit OK the screen goes black and doesn't start (I can still exit out though).