I play heel up most of the time. Sometimes heel down, although it isn't really a conscious decision...I just switch back and forth somewhat at random, it seems. There may be some correlation with how bored I am with the part I'm playing. Also, if I'm trying to go all super fast, my heel is down. When I first started on drums, it was heel down because I didn't have the stamina to play heel up and didn't know any better and then I heard all this business about how much cooler you are playing heel up. Now my heel is just confused, I guess. I can play wearing pretty much any shoes that have some traction so my foot sticks to the pedal.