My family does. Interestingly, the most ardent and consistent fan is my two year old, who'll sit on the coffee table with a wiimote in one hand while watching TV. He'll glance at the WII ever so often and flick the wiimote to "participate" in whatever he's got up on it's screen. My ten year old plays a couple times a week but it gets a serious workout when she has friends over. It is engaging enough that my wife's planning the kids a WII party and has tasked me with buying two more remotes as well as a new game (Mario, I think she wants). My teen came home on Spring break and had a whale of a time playing with her siblings.

Instead of seeing diminished use over time, I'm seeing the opposite. I, like the OP, had basically stopped playing after the first few week but the toddler has literally dragged me back to the WII and I now do find myself happy to spend a couple of hours with him on it over a weekend. I really do wish he'd stop thinking that 2:00 a.m. is a good time though...

Just in case I've given the impression that I've got screen-fixated, all-geek kids, let me hasten to note that the college kid sings, did the dance troupe bit, and parties hard with a (seemingly) alright clique, while the ten year old bikes, sings, roller blades, plays with bugs(!), does gymnastics and studies drums, piano and guitar. The two year old is active enough that my wife is insisting that we start him off at martial arts next year in hopes of bleeding off some of the boundless energy that makes watching him a tag team effort.