I currently ride a 03 Kawasaki ZX-6R. Having grown up riding dirtbikes it took some getting used to, but it's not all that bad. I've done many rides that were several hours long (some were all day with stops only for gas) and my butt was a little sore, but it wasn't terrible. FWIW, the ZX-6 is known to have the most aggressive riding stance making it a little less comfortable. I've ridden some of my buddies' Hondas and Suzukis and they were more comfortable than mine.