My general thought is that in a full service restaurant, the bussers and others share in the tips. So I should leave something to cover the service I did get. If it's really impersonal (on the level of a busser just dropping off and clearing), a couple of $$ is fine. I'll often leave a dollar or two in a Smashburger or other "fastfood" restaurant that delivers to the table and clears after I order at counter. This is similar in my opinion. If a more personal level - someone checks on our satisfaction, explains menu, explains iPad, makes suggestions, a more normal level of tip is appropriate.