I use this one:
http://tinyurl.com/2cn3jn [cabelas.com]
I have no real complaints. When I bought it I knew what I was getting into... I wanted a smaller pack that would be lightweight and easy to wear. I saw it as a bonus that I would have to reduce my gear because I had entirely too much. It has two internal pockets, two on the outside, and a zipper pocket in the back... Holds two small fly boxes and I can occasionally get a bigger one in the back pocket but it's uncomfortable and a hassle.
All in all, I'm probably going get a bigger one for exploring uncharted waters and keep this one for more known places where I can get by with a box or two of specific flies.