I've never tried one, because since I don't have a decent camera phone (flip fone with 1.5 mp camera ~ ha!) there's no way I could be discreet in the restaurant.
Even with a nice camera phone, how do you get "up close" photos of menu boards, which are usually behind the counter over the employee's heads, discreetly?!
Although I do like Lelou's thing about taking it to recommend to someone.
Practitioner of the Nerdly Arts.