I'm pretty happy with my Timbuk2 bags although it took me a while to find which size was best for my needs. I agree about the waist strap, it's essential. I also wear my bag with the strap really short when I ride, so that it doesn't rest on my butt so much as my lower back -- otherwise I find that it catches on the saddle if I have to dismount. (I usually commute on a Brooks saddle, and I don't seem to have that problem on my other bikes.)