I did exactly what Maack did. But I've had 2 ds and 3 psp's (this one's my 3rd). And I downgraded it from like 3 something to 1.5, it was totally crazy, and then upgraded to CF 3.40 LE. And it is totally great man, you can play psx games on it as long as you have a high memory stick (2 gb-4gb, if you're lucky a 4gb is like $30?).
I know a few here have Nintendo DS and they enjoy it, modded or not. And I would agree it's a great system! Definitely innovative. But the only games I found entertaining were Animal Crossing and the new Super Mario Bros game.
On psp it is just so easy to download and put whatever games you want on it. Movies are easy too, just convert them and put em on and they're ready! Psp can even play some n64 games through emulation, which is amazing and at pretty good speeds right now! It's all worth looking out for!
I really think someone else with a DS and modding experience should speak out about their experience, give Retro another perspective on it. We have to be fair with Retro!