DS Daily: Je ne sais quois

That special something -- the DS has it, certainly; the dual screen handheld is slowly taking over the world. Sales charts everywhere are packed with DS titles. The systems themselves continue to outsell everything and hell, everyone already has one ... including your mother.

So what is it? What is it about the DS that has made it universally popular? Nintendo attributes a lot of the success of the DS to Touch Generations, and while that's certainly had a huge effect on sales of the system (and in widening the market), that can't be everything. You aren't listing Brain Age as the reason to own a DS ... are you?