I just installed my Heli bar risers. Purchased from Indy Superbikes. They're a 3/4" rise. There definately is a difference, but with only one ride on them I'm not so sure that the stock height was even uncomfortable. So while I will probably leave them on, they did not make an "OMG!" difference. My only complaint is that there is a pretty ugly "hole" in the middle of the bar clamp now. Seems that for $80, they could includ some kind of plug....
I'd give them a 3 out of 5 stars.