Come on, people. The Mayflower sucks and has for years. Old, crappy rooms, surly staff... There are dozens of superior hotels in DC without the attitude and drawbacks. Heck, the Ren on 9th St is superior in every possible way.
Some of my other favorite Ren's have already been mentioned: Las Vegas, LAX, Broomfield, Lodge at Sonoma, Baltimore. I also like the Boston Waterfront, Philadelphia Airport, and Portsmouth, VA. Some that I liked but that are no longer part of the chain are Orlando (not the airport--that one sucks compared to the FS Marriott across the street), and Wailea (although it went seriously downhill in its last few years).
I have always wondered why the San Diego Marriott Gaslamp Quarter is not actually a Renaissance. It has the quirky, unique character, outstanding location, and proximity to another FS Marriott that often are the hallmarks of a great Ren. Does anybody know why it was branded as a Marriott and not a Renaissance?