My reaction to Potbelly is always "so small," followed swiftly by "so good!" If you're looking for a direct Subway substitute, Potbelly will come across as pricey. If you're looking for an alternative to chi-chi $8-$10 sandwiches, Potbelly uses highly respectable ingredients and has a wheat roll that toasts up delicious.
The Wreck is a truly fine sandwich, nicely filled and tasting like cold cuts I would not be embarrassed to buy at the supermarket.
The environment is also a bit more soothing than many sub shops: it's all earth-tones and wooden chairs, so there's a sense of relaxing.
The clerks are cheerful even under the pressures of customers with truly peculiar orders.