MAME4droid has just been released and works pretty well. I have it running on CM7. Seems pretty well suited to a tablet. The touchscreen controls work better than I expected, but still fairly limiting. Easy to miss pressing the controls with no real buttons or stick to feel. Quite a few games don't work but many more do. I may need to mess with the MAME rom set some more.
Getting my MAME fix on the go has never been easier! I give it a thumbs up.
http://code.google.com/p/imame4all/