So far, what I've been reading looks pretty sweet. I thought at first that the PSP was going to blow it out of the water, but then I found it it would be compatible with the GBA, plus that touch screen is like having a mouse, making it the ultimate portable system for first person shooters.
I'll probably end up buying whichever system gets the best modchips and emulators, because I love my portable system to do more than just play games.