The ones I've ridden (Iron Wolf and Mantis), were both terrible, and my both beat up my head and my legs. The GP loves them, though, which explains why I had to wait 45 minutes for Mantis. However, there are some stand ups that don't appeal to the GP, like Iron Wolf wasn't a big draw, if I remember correctly. Now, I will only ride a stand up if I only have to wait less than 15 minutes, or if I need the credit.