As other reviews have mentioned, the turkey is really the highlight here at Capriotti's. I'm not usually a fan of turkey sandwiches, because sliced turkey tends to be kind of dismal, but Capriotti's turkey is pulled and it makes for a delicious sandwich.
The other things I've tried have been good too. The roast beef is nice, although it doesn't crush its competitors as convincingly as the turkey does. The Capastrami (hot pastrami, coleslaw, Swiss cheese, and Russian dressing) was a little odd but perfectly edible. The Swiss cheese was essentially undetectable, but that's okay with me since Swiss is probably my least favorite cheese.
All the subs are served on great bread (soft, but still substantial enough to not fall apart after being inundated with mayo and piled high with fixings) and come in one of three sizes (9, 12, or 20 inch). The prices are very good, so even a sub capable of feeding you for two days is affordable.
Capriotti's seems like the kind of place that would do well downtown. There's not much reason to go out to the far west side where they're located, but if you ever find yourself out there, you should definitely stop in.