I expect (or at least hope) to be comped only if there's something seriously wrong with a dish in a high-end restaurant, as when my brother's chicken was partially raw at lunch at Bouley and had to be sent back. In the instance mentioned above, we tipped as if we were charged for the dish. In circumstances where the comping was totally gratuitous, I've added extra on top of what I would have tipped on the whole bill. Do I expect a freebie just because it's a birthday or something? No. A candle in my dessert, yes. Considering that there are restaurants that have a high volume of celebrators every day, do you want them to go broke giving everyone freebies? I definitely think it's presumptuous to expect a freebie under such circumstances. My feeling is that if I get one, I'm thankful, but I never expect it or take it for granted, and never try to pressure anyplace for a birthday gift. I think that's gauche. Then again, I also don't let restaurants know what the occasion is; usually, someone else does, though. But all I want is good food and good service. My friends can give gifts if they like, but the restaurant has to make money and deserves full payment for services rendered.