I'm not bored with the demo yet; I'm still trying to learn new combos and it seems like I'm figuring out new stuff everytime I play. Plus I play it with some friends and its always funny seeing their reaction since they're so used to Street Fighter.
Good point. I think it really depends on what characters you like. For instance, I can't get enough of Johnny's sexy mug. But if I were a big cyborg fan, I'd probably not play the demo as much as I actually do.