My kids each have one (1 white/1 pink) and I gotta say, the system itself is fantastic! Coupled with a top-notch game (like New Super Mario Bros) and it is a great little game system. Some of the games we've bought are stinkers (got bass fishing and texas hold 'em real cheap and they weren't worth that!), but most are very good to great. The kids love Nintendogs, Super Mario, Mario Kart, and Animal Crossing: Wild World. The wife loves Brain Age. I think I'll get her Tetris DS too.
I read somewhere recently that the DS is the #1 game system in England.