I've been having a good play with all the various emulators etc. Basic rundown of functionality of the "best" ports for a given hardware set seem to be;
PSP-Mame (v0.96) - functional for a select few ROMs, but little if anything is currently at a playable speed. (Except very old very simple games)
RIN - Works very well, games seem to fun at full speed for Gameboy & Gameboy colour.
PSP Genesis - Works well, PSP screen or the emulator itself seems to have some issues keeping up with Sonic the Hedgehog ;)
NesterJ - Works very well. Good old Super Mario Brothers ticks along at a solid 60fps.
SNES9x - Works, runs most things okay, but framerates are seriously crippled on all but the simplest games.
With most of these having new releases every couple of days, it bodes well, and should make the effort it took to get a 1.0 PSP well worth it :)