This is the first JJ's I ever went to, and I instantly loved it. Its a chain and its not the same type of sub as Dave's across the street, but its still great.
The bread is actually the secret ingredient of a Jimmy John's sub; something about their french bread is extremely appetizing. The rest of their ingredients are pretty high quality, although not mind-blowing. As the other reviewer indicates, they are pretty simple overall.
Seating is plentiful, the hours are good, and the prices are quite reasonable. When I go back to Cleveland, Jimmy John's is one of the few places that I allocate more than one meal at (have to make the most of my meals!).