Good base for exploring DC
Overall I enjoyed my stay at this Westin. The room was very quiet, spacious and comfortable, a nice oasis to return to after long days walking around Washington and taking in the sights. The bathroom was huge, also a nice plus. There were a couple of details I felt were overlooked though - hanger for bathrobe in the bathroom, but we never got the bathrobe; checkout said 3pm in the in-room guide, but was actually 12pm; told I was being charged for a newspaper each but I never received one - saw later they were just laid out by the elevator - so why was I charged? Small things, but as I was staying a 'preferred guests' room I expected more consistency from a hotel of the Westin's class.
Location was very good - directly on the Circulator bus to Georgetown and other areas (only $1 per ride), 20 minute walk to the White House, and served by the Metro (direct line to Arlington Natl Cemetery, DCA airport, all major sights in the city) via the Foggy Bottom stop, which is a short but somewhat circuitous 10 minute walk away. If you have lots of baggage or are traveling during rush hour, I would skip the Metro and take a taxi to/from DCA - even in traffic, it was only a 20-25 min ride and less than $25 - otherwise, the Metro is very efficient and a great way to get around what is otherwise a walker's city.
The immediate neighborhood isn't that interesting, but there is a 24-hour CVS nearby for snacks/drinks/etc and it's a very easy walk or bus ride to Georgetown and other areas, so that didn't bother me too much. 
Overall, the Westin is a very solid and comfortable place to stay, maybe lacking a 'wow factor' but relaxing, away from the hustle and bustle but still convenient. I would consider staying here again if I got a good rate.