bit of feedback from mine (which arrived last Friday), it works with all the games I tried out (and I tried a lot!).
I used it for probably 40mins and then I got tired but you can easily turn it off (there's a button next to the thumb stick). I love the idea though, I think i'm going to use it for all of my games (until i'm tired) and then just turn it off each time. At least i'm doing some fitness each time I decide to go on my Wii! a step in the right direction I think.