I recently had a good experience with Potbelly in Chicago, and decided to check out their east side Madison location while running errands. The store is nicely decorated and kept up, and the staff was very friendly.
I decided to repeat my order from my previous visit, but upgrade to the "Bigs" - a larger sandwich that would allow for lunch the next day. I opted for the turkey but subbed cheddar for the swiss and had lettuce, tomato, pickles, mustard, oil & seasonings. Everything was fine except for the sandwich maker being super stingy with the sauces. I know he didn't miss them because I saw him pick up the bottles, but I could only taste mustard on one bite. Overall everything was on the dry side. It was a fine sandwich, but skimping on mustard and oil & seasonings seems silly since neither is a premium item.
You get a lot of food for a low price so I'd definitely stop here over Subway, but next time I'll ask them to go heavy on the mustard.