Its been a while since I've updated this thread - so there's no time like the present.
I came across this pretty cool site that appears to have been created by a Mac fan and in addition to hosting MAME ROMs, they also have a page that details setting up a dedicated arcade cabinet that's powered by a Mac Mini and a PowerBook. It definitely makes for interesting reading.
Man, that guys site is GOLD for working MAME roms for MameOSX!!!
Thanks for linking to it!