I have a mixed record so far. After a nightmarish stay at Motel 6 (where stays don't get too much better than "not uncomfortable"), I filled out their online complaint form. No phone call or response from them, no acknowledgement even. Then three weeks later, a voucher in the mail came for one free night at ANY Motel 6. Good job guys!
Two years ago, I was in endless phone conversations with Marriott after their awful catering at the 2009 Stoker Awards. (I thought it was awful.) They were very polite and detailed, asked a lot of specific questions about what was wrong with the food, claimed they'd retrain the entire hotel staff. But no money for me in the deal. Not thrilled with that, but I guess if future guests are happy, I shouldn't be too upset.
Well, this time it's La Quinta's turn, after they kicked me to the curb on the second evening of a two-night stay, claiming my reservation was for one night only. When I proved that no, it was for two nights, it says right here on every piece of paper you've given me, then they had to pay for my hotel elsewhere, but it was a pretty big hassle, driving to the other hotel (with all my belongings in a trash bag) and then back in the morning for the conference. We'll see what they say!