What can't be faulted: Food and coffee are terrific. Especially the coffee. Also, I have been seated very quickly at each visit. The servers are delightfully cheerful and Joe himself comes out to speak to each table directly. It's a high-quality, old-school diner experience and well-worth the minimal price.
What is a bit of an annoyance: By applying all of that personalized service, the speed of the service suffers when they are even a bit busy. I don't believe Joe has enough help behind the line, and it's probably further hurt by his zeal for customer interaction. And it seems that maybe order turnaround time might be slowed by the apparent lack of any computerized order management/POS system. When get your check you're supposed to pay your server, but if she's not around and you go to the front desk (because you need to get on with things), you won't find a dedicated cashier. Just a hostess. Who is very nice and cheerful.
It could be that this is how long service took back in the day, and I have been spoiled (with the other members in my party) by the super-speedy almost-flawless delivery of cold, corporate places like Chili's, Denny's, Applebee's, and other places who have teams of industrial engineers and MBA's to hone their model. In that case I fault myself. I barely remember how things were back in 1978 or whenever.
I remain a fan and will return, but will need to keep in mind that Joe's requires more of a time investment than do other places.