It depends, for me: sometimes a backpack works, sometimes not. For short trips or carrying light stuff (clothes, tennis rackets, or sparring gear), the backpack works very well. For longer trips the tankbag or rear bags (tail- and saddle-) work best. The rider needs to figure out what works best for him/herself.
Originally posted by GixxerChris I did lay on the tank bag, but going 100+ mph trying to keep up with the zx12r and zx9r whipped my head back and forth badly because my head stuck up too far over the top of the windscreen.
Riding around with the right motorcycle backpack shouldn't be an issue at all. Actually, their materials are more heavy duty (to withstand the air resistance) and usually they have more features that are motorcycle-related (back protector, hyrda pack,....etc)