The local Chili's was a test store, and has been using tablets like these (Ziosk brand) for a couple of years.[0] A few people might complain, but generally they seem pretty popular and well received. Kids entertain themselves with games, and the adults can pay and go whenever they're ready. I never noticed a reduction in waitstaff, but turnover was much faster when the restaurant was busy.

[0]http://www.forbes.com/sites/alexkonrad/2013/09/17/chilis-to-...