>You're not obliged to pay tips here is US too, if you don't like the service.

good, that's reasonable. :)

>>>My husband and I usually do this way: if we don't really like the service (say, we waited too long in the restaurant) we pay 10%, otherwise we usually pay 15-17%.

now this is something different in the culture: in Brazil, the tip is already added to your bill, and it's always 10%. People *really* satisfied with service might give a little more than that, but it's quite unusual. And if you really didn't like the service, you don't have to pay the tip at all (well, of course some people won't like that, but I don't care... all I care is my satisfaction as a customer). :)