I've stayed at this location for work a few times. If you need a clean, less expensive room in Ballston/Arlington, this is your best bet.
It is not a traditional hotel. So if you want fresh towels every day, a hotel restaurant and bar, feel free to pay $200 more per day down the street. A bar or restaurant isn't really necessary anyway, since you are within a short walk to about 30 options in Ballston.
What you will get is what amounts to an apartment. Each unit has a full kitchen. It also has a washer/dryer. I was able to wash my clothes before I left, which was a huge convince. They also have a rather elaborate workout area, complete with treadmills, elliptical machines, kettle bells, free weights and even a bench.
They also have a nice lobby area, and a pretty sizable market where you can buy water and other options at any time of the day with a credit card.
Oh, the staff is great!
Be warned. The lower part of the building is student housing for a local university, so you will encounter 20-somethings, and possibly deal with noise on the weekends.
Really, I only have two complaints. They require you to fill out a bunch of info and scan a photo id before you arrive, which was mildly annoying considering they ask for your ID at the front desk. My only other complaint was that they didn't have cleaning supplies for residents to clean up for themselves, which would be nice since service is not everyday. That honestly is about as minor a complaint as you can get.