I have been mostly playing PSP (Tekken 6, MotorStorm: Arctic Edge and soon Final Fantasy Dissidia), but I occasionally at school play some DS Download Play with two other classmates, who both happen to own DS.
I am planning on re-buying a DS (the Lite model probably...) and Mario Kart DS for it. Until that time comes, I'll be using my little sister's DS Lite. :-D