Do you mean the Springfield Heights buildings? They have an XP multiplier. I have most of them piled towards the edges of my town where I don't have to look at them that often. I've seen some pretty amazing designs some have done with them though, but I don't seem to have the enthusiasm to try and do something special with them.
I do play the games always when I remember, especially the ones with a chance for a multiplier item, and sell the excess that can be sold.