Chili My Soul in Encino, CA proudly boasts that their chilies are all cooked for 40+ hours (they have about three dozen chilis in rotations of 10--always a few without beans and at least one vegetarian.) It's generally good but with so many varieties, there are bound to be hits and misses (thank goodness for free samples.)
By "slow-cooking" do you mean braising, or using sous-vide?
Most restaurant, to my knowledge, offer some version of a braised meat. The shortribs at Lucques, pork shanks at Literati II, the shortribs at Hatfield's are some that come to mind.
As for sous-vide, I know that Hatfield's uses that method for their halibut, and Sona uses it also for various dishes. BTW, sous-vide is a method of cooking where you vaccuum seal the food item and slow simmer it.