One of the best stays I've had in a hotel was at a Marriott in Colorado Springs, when I was there for a week on business. This was a couple of years ago, before I discovered Priceline. I was there on a reduced room rate, because I was visitting a large local corporation. Even still, the service I got was fabulous and I think I can agree with some of the previous posters that it was mostly due to attitude. I smiled and was friendly with the staff, and made a point of filling out comment cards on the people I interacted with (and let them know that I would). Always positive and always a rave, and the people that worked there really responded. I did get the understanding that there is monetary value in good comments - no one said it outright, but there was some subtext once that gave me that impression. So - it is always worth it to comment positively.
