We were staying in Soulard on holiday from England and, based on good reviews, visited the Deli. It lived up to the billing. We loved it.
Good ambience, polite and friendly staff and very tasty sandwiches. I really liked it and I can be a fussy old Englishman.
The only problem - it's not found the corner from where I live (in England)!
I hope to visit again someday but in the meantime visit it if you are a tourist and enjoy it often if you live or work locally.