Location, Location, Location
I have stayed at this hotel several times during the past year and it is routinely bustling with a mix of business people and tourists. The bell men do a very nice job keeping traffic moving through the entrance and are always prompt in offering assistance. Depending on when you check in you may have to wait for a few minutes but to Hyatt's credit they seem to do a nice job adding staff in the reception area when needed. This hotel has a grand lobby that is well maintained. The rooms are clean, the linens are of high quality and the feather pillows are perfect for a good nights sleep. With the exception of suites, the rooms are far from grand in size. As a Diamond Member my room was on the Grand Club level on the interior of the hotel with views of the interior lobby. 
The key card system at this hotel seems far from perfect. I had to have my keys reset at the desk during my previous visit and could only get the card to read in the elevators sporadically during this stay. (You only need a key in the elevators to access the 12th floor) While I was checking in, the woman in front of me commented that she was in line for the second time during this stay due to key card issues. 
FYI -The Grand Club is scheduled for renovations this summer. The current facility is more than adequate and the food quality is what you would expect. It would be nice if they offered some hot appetizers or warm breakfast items. During this visit the Grand Club staff seemed more interested in ensuring that guests belonged in lounge than replenishing food or bussing tables. I was twice asked for my name and room number. Considering the fact that guests must use key cards to access the Grand Club it seems unnecessary to drill guests for name and room number. When the host could not readily find my name on a preprinted list he asked if I was sure that I was entitled to Grand Club access. Not a big deal but it certainly did not make me feel like they valued my loyalty. They seemed to be rationing desserts and did not replace the more popular selections.
The best part about this hotel is the proximity to the metro that can be accessed without leaving the building. It is nice not having to step outside in inclement weather to catch a train. This location is on the outer edge of Chinatown and is within walking distance of dozens of fantastic restaurants, bars, movie theaters, Lucky Strike bowling, shopping (H&M, Macy's etc) and the Verizon Center. The tourist attractions off of the National Mall are also within walking distance. One of the key things to understand is that most of the tourist attractions are collocated with other government buildings. This means that after business hours there is not a lot of activity or entertainment near the museums,monuments etc. The location of the Hyatt gives you the best of both worlds; access to tourist attractions and restaurants
Other hotels to consider in close proximity... the Renaissance (Marriott) has larger rooms, a modern lobby and more impressive food offerings in the concierge lounge. The Embassy Suites is ideal for families and offers free breakfast without status.