I just got my first pair so I haven't had a whole lot of time to try them out but so far I really like them. Mine are North Face that REI had marked down to $25 a couple weeks ago. They're comfortable and lightweight and I like the idea of just carrying legs in my pack instead of a whole pair of pants if they are needed or just throwing the legs in my pack if I start out with them as long pants.

Cabelas recently had some of the Columbia zip off pants in the Bargain Cave for about $20 or $30. They may still be available online.

I will be getting another pair or two of some kind of convertible pants at some point. Seems to me to be the best of both worlds.