I've had mine for 2 years now..... LOVE 'em!
Purchased mine from Chilhowee Leather http://www.chilhowee.net/
They are easy to put on or take off. 3 snaps and 2 straps hold them on. They don't flap, move, nothing. You can get them with pockets, studs, just about anyway you want them. ( Mine have studs and a pocket on each side. I bought a STAR logo concho for each pocket. They look like STAR factory pieces! )
I haven't noticed a change in gas mileage, no noise. The bike doesn't know they are on there......
They really block the wind off of your legs and feet.
Plus, they dress up the bike too!!!!