I agree with the tipping problem, I myself try to tip based on the total value and not what I pay (because that may be just for a few drinks). I don't want the waiters to suffer for the business owners discounts :)

Here in Czech republic we have local variants of Groupon and in some restaurants people reported the despise from waiters too. Surprisingly, this did not happen when we went to one that was otherwise really expensive - the people there were very nice and friendly. We won't return there regularly because it's out of our price range but for special occasions I would like to go back.

Regarding the quality - from my experience it's about 50/50, some restaurants are bad, some are ok so maybe contactdick was unlucky in encountering the wors first.