Craig street is the go-to location for students seeking some better quality dining than what is often available on campus (CMU). As such the lack of a place to stop in and quickly get a cheap burger to go was glaringly lacking.
The Bagel factory fills this niche passably. The food is okay, what you would expect for average 'quick' food by a college campus. The option to have your sandwich or burger served on a bagel instead of bread is interesting, but in most cases this ends up being too heavy for the sandwich - I'd recommend sticking with the 'normal' breads.
The bagel factory is a good choice if money and time are the deciding factors for you. If you've got the money to spend, Eat Unique down the block might be a better choice. If you've got the time as well for a sit down meal, the union grill might be a better option.