I always take the Vamoose bus.
What I like about this bus service is the convenience of the parking lot in Bethesda and the fact that the bus always leaves on time. I'm able to park in the long term parking lot and wait for the bus under cover. There are several daily times to pick from and the price will vary accordingly. I have never had a "break down" or air conditioner problem but my daughter has in her travels back and forth from NYC. The bus Wi-Fi service is slow but it's there and the plug-ins for charging are convenient. I have always found the drivers and check in personnel courteous and competent. They have even helped me hail cabs in NYC. I definitely recommend this bus service.