Had a great stay for a seminar I attended in late April. The hotel is basically two doors down from Hilton headquarters. Was immediately greeted by the bell man who helped me with my bags, and patiently waited while I checked in. He then took me to my room. Enjoyed this classy touch.
Rooms are clean and modern. Bathrooms were as well, with a nice glassed in shower. The conference rooms were large, although like all conference rooms did get a little chilly. You will need a car at this hotel, I didn't see anything in easy walking distance, and the hotel is located in a business district which wasn't walking friendly. Parking is free.
I enjoyed my stay immensely, and highly recommend the Hilton McLean Tysons Corner.