I often think that the key to Subway is who's making the sandwich.
The one nearest me is operated during the day by the manager, a woman of about 50 or so.
She's clean, the shop is clean and the ingredients look fresh.
On the other hand, the shop in the next town is run by a group of teenagers who couldn't care less about the food or the job as a whole, they're busy grab-assing; I won't go there.