I like the 5.11's a lot. I can get away with wearing them to work, as our dresscode simply states 'black pants', not dress pants. I find them very durable, very comfortable.
I have them in black, coyote, tan, and bizarro 5.11 desert camo that I got for 7 bucks.
LA tactical has the brown ones for around 10 bucks, last I checked. Every size but mine, of course.

I also have tried the Woolrich line of tactical pants. Lighter material. No problems, but I did rip a pocket somehow, maybe a week into them. Never ripped my 5.11's, to date.

I also wear the 5.11 academy sorts just about exclusively, and I still have the old style billy goat shorts kicking around.
If any of you guys remember Magnum PI, he wore billy goat shorts quite often.