A few quirks, otherwise excellent
The Westin Georgetown is not actually in Georgetown. This may or may not matter to you. It was not an inconvenience to me, but confusing when I realized that I was closer to the George Washington University Area and Foggy Bottom than to Georgetown. That said, it's in a great neighborhood, about a 5 minute walk to the Metro, about 30 minute walk to the Lincoln Memorial. There are restaurants in the area, and a CVS drugstore for necessities.
I stayed for four nights in August 2012. 
The GOOD
Staff -- room service, concierge, front desk, etc. were extremely professional and courteous. They could not have been better.
Cleanliness -- the public areas and my room were spotless
Bathroom -- as other reviewers have mentioned, the bathroom was renovated and had a separate shower with two shower heads, a soaking tub, solid surface counter...
Quiet -- my room was dead quiet. No noise from the hall, from neighboring rooms or from outside.
Good gym -- the gym is well-equipped and clean with treadmills, recumbant bikes, weights, yoga mats, swiss balls, etc. There is an outdoor pool that I did not try. The hotel also provides new condition New Balance workout clothes and shoes for $5 rental. 
The NOT SO GOOD
Weak water pressure -- This is an old building that has been renovated to make it a Westin. As is common in older buildings, the water pressure was extremely weak.
Strange layout -- My room was at the far end of the hall, the equivalent of about a city block length from the elevator. I wonder if there used to be a back stairway or some other way to access the end rooms. 
Lack of HD channels -- OK, I'm being picky here. There was a nice HD television in my room but it only had a handful of HD channels. Most of the channels were Standard Def. 
No restaurant -- The restaurant was under renovation so there was no on-site eatery. There was a temporary (I think) bar set up in the lobby, but it was far from cozy. Room service, very costly, was available and good.
AC blows on the bed. --- The Westin has an energy saving feature that turn off lights, the television and the AC when you leave the room. This worked great, however when the AC is turned on it blows right on the bed, at least in my room which had a single king size bed.