i only use my backback when I go to work. I have a fulmer v2 helmet that has that goggle strap on the back, sometimes the top handle/strap on the backpack will get caught on the goggle strap and I cant move my head up, down, left, or right, It sucks.
My helmet used to get caught on the grab handle on the top of my backpack too... i cut it off.
I only wear a backpack if I'm going to the gym on my bike; but while I'm in town I'll usually run an errand or two if it's my day off - i find having a backpack (even if it IS full of sweaty clothes) to be awfully handy for hauling stuff home.
I could care less if people think it's ghey, function over form.
It's just an inexpensive mesh, camo patterned backpack i bought at Academy.
When I didn't have saddlebags, I had a choice of 2 T-bags mounted backwards (not hanging over the rear fender) that looked a lot better than a backpack. If I had to carry stuff inside with me, that's another story.
However, I wear armored jackets so a BP would be a pain in the butt.
A huge part of riding is the freedom. I ain't never gonna wear a backpack on a bike. I also don't have all kinds of electronic devices strapped to me or jammed into my ears; don't wear a watch, either.
Backpacks are cheap and handy when you need them. Deff. not that comfortable on a hot day, but I'm wearing a leather jacket anyway.
There is nothing ghey or uncool about them (unless it's your daughters Sesame Street backpack that looks like Cookie Monster)
Bottom line...it's just another tool. and it gets the job done