We loved it. The location was fantastic and the dock staff was very helpful. The only downside was that we had no cell service and the wifi wasn't very strong. This normally wouldn't have bothered us (in fact it would have made the stay better) except that we had a problem with our generator that we were trying to resolve via phone).
The stay at the marina was great. The booking experience with Dockwa was not. Dockwa collected the 3 nights slip fee from me, but the marina had no idea that anything other than the initial night has been collected so they charged me (and effectively double-charged me). Now I have to work to get the money back. Summary - I will definitely go to Onancock again but I won't use Dockwa to do it.