Yes I've done a lot of work on MAME4ALL and on XMAME.
I have MAME4ALL versions for GP2X, Wiz, Dingoo A320, A380, Nanonote, GCW-0 and Pandora.
And XMAME versions for GCW0 and Pandora.
MAME4ALL is now very mature - I've updated almost *everything*, CPU emulation, sound emulation, 90% of drivers plus a large number of new games to play.
Most games run as if running from a much later version of MAME though still as the same fast speed as the original MAME4ALL. Some of this attention-to-detail may not be noticed by casual gamers however it's been fun making games work on the relatively slow hardware for today's standard.
I wanted to add Gemei A330 to the list - hoping to get this sorted out.
EDIT: Oh yes and MAME4ALL for the Zipit Z2.