Potbelly is ok, but I don't like them nearly as much as other places. Their sandwiches and shakes are both good, but mostly average. I'm in love with the cute little cookies they put around the straws. It's a silly small thing, but I love it so.
The thing that really stands out about Potbelly is the atmosphere. It's really comfy and perfect to relax in. I would not say the same for almost any other sub shop.
If you're looking for quality, go else where. If you're looking for atmosphere, this is the place you should go for subs.