I concur with OP and after running a restaurant for 2 Sims generation, I would like to add:
1. I don't have any extraneous objects that would distract Sims. No pianos, no stereos, no chess sets, no computers etc. I found Sims still got up and chat with each other but they returned to their tables much quicker if they were not distracted. I don't even put bars in my restaurants although they're maybe ok (don't know, haven't tested this).
2. If you use any custom content (especially tables and chairs), make sure they are updated for Dine Out pack. I used custom tables once and they really bugged out the game. I had once a bug where I couldn't customize my Sims staff's outfit. The culprit was CC. As soon as I deleted those CC from my lot, outfit customization was fixed.
3. Use the automatic garbage can (I can't remember the name) instead of the "manual" garbage can that needs to be re-emptied into the outdoor trash cans. Delete all outdoor trash cans. It saves your Sims staff from having to take garbage out and other sims from wanting to kick the outdoor cans (and you/your staff have to clean up after them). Your Sims staffs should be focused on doing food related things as much as possible.
4. Pathing: I now prefer to build my own public lots (whether it's retail or restaurant or gym). When I build my own I do not use MOO (I still use MOO for my Sims' house).
