Can someone get the resolution right?
This was the only thing I thought the Amiga MAME version was BETTER at than on the PC. Getting the resolution right. On CyberGraphX, I could use CyberMode and define any screen resolution I wanted... Even the original arcade display mode, and put that into an acceptable frequency range for my monitor and get a perfectly aspect-ratio fixed and naturally scanlined display. :-)
Sure, the PC picks a suitable resolution automatically, but it's usually a mediocre mode, at best. Most games have large black borders or look very blocky because of doubled pixels.
Of course I've only messed with earlier versions of MAME under CyberGraphX. If you're relying on AGA or P96 you might not have as much luck. (And if you don't have a PPC, good luck playing anything more complex than PacMan.)