Stayed one night at the Crystal City Marriott. We were supposed to stay 3 nights at the Marriott Crystal Gateway, but they were overbooked our first night. Gateway offered to either honor our reservation or they could offer us a free night if we moved to Crystal City Marriott for one night. We agreed, since it would save us around $120.
Pros at Crystal City Marriott: friendly staff, comfortable bed, very clean room, and spacious bathroom.
Cons at Crystal City Marriott: Room 230 smelled like it used to be a smoking room (all rooms are now considered non-smoking), and was right above the hotel entrance and stop light, so you heard the traffic and buses stop/go all night. The air conditioner was loud and kicked off/on often, making a clunk noise every time.
Overall, the hotel is in a good location with access to the CC metro stop by taking the elevators to the garage level. The rooms are clean and comfortable, but not very quiet. The staff was very friendly and accommodating.

We stayed at the Marriott Crystal City Gateway for two nights-2 adults and 2 kids, ages four and six. The shuttle from the airport was convenient and quick-both ways. We were able to check in at 2pm after our flight arrived, freshen up, drop off our luggage and hop on the Metro into DC. The Metro station is attached to the hotel through the underground mall. There are several kid friendly and good restaurants right in the area--within a few blocks. We really did not get a chance to explore the mall. The Metro was, of course, key to getting into DC for the regular government sights! The pool is great, with a full-time lifeguard, there are adequate changing rooms and a small fitness room as well as some equipment in the pool area. The pool and fitness room hours are until 11pm and start early (630am?). The room was spotless and the staff went out of their way to be helpful. CC BIstro is EXCELLENT for breakfast--waffles and omelets made fresh and a full buffet-so make sure you include breakfast in your room. CC Bistro was also good for dinner for all of us. No noise issues but the hotel was not full. Overall a great place to stay and tour the city (cheaper by about $30 night than the in-town Marriotts)

Marriott Crystal City is a great place to stay. I was there for four days. The staff was very friendly and the hotel is located in a safe area. Its best feature, however, is its close proximity to the metro. The underground walkway (metro to hotel) is safe, clean, filled with shops. I will definitely stay here again.

We enjoyed our stay at the Crystal City Marriot this past July. It was convenient to everything we wanted to do.

On the positive side, the hotel was in excellent condition, including our room. Being connected to the underground walkways was especially nice. It was a short walk to shopping, restaurants, and a Rite-Aid pharmacy, which came in real handy for a few odds and ends that would cost much more elsewhere. In addition, the walkway connected to the Metro (Blue Line), which was our transportation into DC each day. The staff was very helpful and attentive. Check-in/check-out was a breeze. Since we flew out of Reagan National, the hotel's complimentary airport shuttle was terrific.

On the minus side (a minor 'minus'), I would have liked it just a bit better if there would have been complimentary internet access.

Would definitely stay there again at the rate we obtained ($109 pn)