Good location, but bad value for the money
Stayed here this past weekend for a Girl Scout event in DC. As other reviewers had said, this place needs attention, as it just seems old and outdated and just not up to what I would think is the hilton standard (and the elevator was perhaps one of the slowest I have seen). There were also a number of problems we encountered. The ice machine on our floor did not work, there was supposedly coffee at the front desk, but every time we went, they were out.The pool was small, but it was neat it was on the rooftop. However, on multiple trips up, there always seemed to be numerous college age guys hanging around, coolers full of beer, playing music and having their own pool party. They were generally using foul language, and even had a "blow up doll" they were throwing around the pool, while also sloshing beer all in the pool. They didn't seem to care there were young girls around, and while we called the front desk numerous times, and were told they would send someone up, nothing seemed to get done until the guys eventually left on their own. My final comment is that the bellhops were generally very rude. They gave us a very hard time about not wanting to valet park with them, and the dollies to carry the bags, they did not want to let us use by ourselves (which we use at every other hotel and no one seems to be "possessive" over them). 
Overall, I wouldn't stay back at this location. For the price (close to $300 a night), I would have expected a LOT more in terms of service and apperance (and free wi-fi).