i've done it a coupla times in nyc on new years eve. we aren't very good planners, but have always had luck getting into places at the last minute. on a night like that, you do whatcha gotta do.
i'm extremely lucky with parking too, which is a big help in this city.
it doesn't sit right with me to do it on any kind of normal basis. we generally used to go to places without any kind of preferential treatment anyway at home in jersey.
jersey, for the most part is reservations, then special requests (or very annoying, loud, pushy old people), then first come first served. i guess you can bully your way in with a c note, but otherwise the hostesses and maitre d's will tell you how long the wait is, or if you don't have a shot without reservations. not once has any of them suggested a donation would help out.
the worst you get occasionally was the valet parking in a parking lot mere feet from the door. or the places that give you a numbered card to pick up your doggie bag at the coat check. just ways of getting more tips, but that's no big deal.