I have one of these bloodwych and so far its been pretty good build wise. The d-pad on the black model is slightly higher than the white models so is even better. The d-pad on this is more like a NDS or GBA d-pad than the rubbish PSP one.
Apparently a linux dual boot OS is due for release very soon so you should see a lot of gp2x software ported over including MAME4ALL and hopefully picodrive.
The emulators that it comes with are a mixed bag so far, NeoGeo, CPS1, CPS2, NES, GBA have been not bad at all, SNES and Megadrive need some work. The divx player works really well.