I finally got around to getting zodttd's gpSP source compiling for GP2X, and have ran it on mine as well (via NAND - will setup USB server sometime soon). Tried Castlevania: Aria of Sorrow; it runs fullspeed with frameskip 2 at 275MHz. Not bad, although there's certainly room for improvement. I asked zodttd to let me have a couple weeks of exclusive access to the code so I can optimize it some. We'll see how that goes.
I still need an AC adapter though, these batteries will only last so long. I don't suppose anyone would like to donate one to me? :x