The main selling point for me with the DS was MOST DEFINITELY the price.
I was able to buy one for both me AND my girlfriend. So once the WiFi games start flowing in, we'll be able to play each other. Plus, all the kids in my family are getting DS's for the same reason. So there'll be even more gamers. The PSP is definitely sexier, and I'd rather have one than a DS, however, I don't know anyone else that would purchase one and I REALLY more interested in WiFi multi-player stuff on a handheld at this point.
Your average Joe just cannot afford (2) PSP's for one household...
mrC