I still enjoy my DS, I think it's great hardware. I'm a little disappointed in the current crop of games though. Most of the time, I've got Final Fantasy I&II in my DS, but I know that will change in time.
As far as the PSP, I'm still buying one. I think the competition will be good for the handheld market. And, as said above, it has been a long time since Nintendo had any competition in the handheld arena. This should be interesting.