I stay at this property at least once a month. It is a nice hotel and as a Diamond I have been treated very well. The location is great. I love the Grand Club, including the coffee maker... it may take a minute but it is worth it! They rotate the same appetizers every three days it seems, with some new and generally very good cheese choices once in a while.
Other than that, it may help to consider that this really is a convention hotel. It is a huge property and appears to be sold out quite often, especially during the summer months. Service is not always up to typical Hyatt standards, but that may be a function of the sheer size of the hotel (one of the club concierges is a former UA FA and it sometimes shows

).
For a better overall experience, I would recommend the Hyatt Regency over on Capitol Hill, which is excellent. However, the GM from that property moved to the Grand a little while ago, which should bode well for this property. I exchanged a couple of e-mails with him recently and he seemed extremely friendly and responsive.