I followed a line in from the sidewalk to Qdoba today, a new addition to the Center City lunch rotation. They are open for dinner as well, and there's a branch opening near 40th in University City as well.
Qdoba is like a Starbucks-ified version of a California taqueria. It's got the Ikea-ish style of a chain, good service, good prices and reliable (after one visit) quality. For Philly, it's the best option to walk to from work for a good, fresh-tasting burrito. It's far better than 12th St. Cantina or Hot Tamale.
I had a chicken burrito with the "fiery" habanero salsa (hot and tart) and guacamole (fresh avocado - not from a mix) while my friend had a chicken burrito with a special "queso" sauce which was supposedly good.
Burritos are in the $5 range.
Biggest criticism was the wait (first day, so understandable) and the wrapping of the burrito. It was loose and amateurish, but good enough.
Thumbs up and see you at lunch.