I was actually considering a vita recently. but this thread has me thinking...

I gave up on tablet gaming, even with emulation and control pad support. With the Go, Mame and the entire 8 - 16 bit emulation roster can be had in a great form factor. There's also the ISO thing Chany mentioned.
I would imagine that the PSN store might be off limits with the system modded, but I haven't checked, and I maybe have a handful of reg psp games that I'd want to try out/own.
The price point on them is REALLY good, I found a CIB white one for $70ish.
The Vita looks awesome no doubt, just doesn't "solve" my gaming wants like the Go.