Here in Korea, it's pretty much the ONLY place I can go to get a decent sandwich. It sucks that they only have white cheddar cheese though. I really miss provolone as an option.
I think Subway is pretty decent if you just want a turkey, ham, club, spicy Italian, BMT, etc. kind of sandwich. I can't really comment on the tuna or "crab", since I never eat that. Their bread is pretty good, provided you actually get it fresh. Anyone complaining about it being rubbery clearly got old bread. Their steak subs have never been that great as far back as I can remember. Meatball could be good, but their sauce sucks.
When I lived back in the states last year, a Marco's Pizza opened up near my home that had really excellent subs, especially the steak and meatball subs. I usually went with them over Subway, when I wanted a sandwich. I'm not sure what all the praise is for with Publix subs. The quality of the ingredients was pretty good, sure, but their bread was always way too tough and chewy. Every time. Even when I just bought their bread to make my own subs with.