I've only been to the Rockville SC myself, although I believe the dealership I bought my used Model S from took it to Tysons for something, just before delivering it to me. The Rockville SC told me that currently, they're really "slammed" with customers all of a sudden. They predicted about a 4-5 business day turn-around to work on a few things for my car, but they got it all done in 2 business days. It was definitely very busy, with just about every parking space filled with someone's Tesla.
IMO, Telsa could stand to open a third service center for the DMV area at this point. I believe Rockville was opened to take some of the load off of Tysons, but now it seems to be just as busy!
