Great location for parts of DC, but challenges for families
I stayed at the Liaison with my wife and son for 4 nights, in a room with 2 queen beds. It was extremely convenient to Union Station (we arrived by train), and an easy walk to the Metro at Union Station, Capitol Hill, and the Smithsonian museums at the east end of the Mall. 
However, by the end of the week the small size of the room (particularly the bathroom) left us feeling claustrophobic. In particular, the shower and sink were all in the same room, without an outlet to plug in appliances such as a hair dryer. In fact, we had to move items off the furniture, to have room, and then got charged for drinking the in room bottled water (which was simply stored in the cabinet) - the charge was immediately removed when we pointed it out. Also, the perks - the tour kit, special pillows, and exercise kit - were not really worth the effort; the iPod tour was unexceptional, and the exercise kit needed a DVD player which the hotel had run out of. Finally, the beds were elevated quite high, which I have frequently seen on business trips, but which was uncomfortable for family members.
Also, there wasn't any lounge or lobby area for a quiet place to read or relax. The lobby (with WiFi access) is adjacent to the restaurant and bar, which get quite loud. The pool on the roof was not as bad, and had a lifeguard.
The staff tried to be helpful, and generally succeeded; the concierge Michelle even reached out to us before we arrived in response to a question I had sent about a tour. (We drank a lot of the excellent punch by the front door.) These constructive suggestions did not detract from having a great DC vacation, but from the hotel's reputation, and the praise from a work colleague who had attended a wedding there, we had hoped for a better experience. (We avoided the restaurant because of its prices, in favor of nearby Subway sandwich shops, and our "splurge" meals at the Capitol and the Smithsonian.)