Like many other airlines Virgin have issues with Rolls Royce engines that are on the Boeing fleet. As a result they have been forced to get replacement aircraft in in order to avoid cancelling services. Apparently on a number of the Gatwick fleet they are using Airbus A330-200's purchased from the now defunct Air Berlin. These aircraft are yet to Virgin standard (according to the stewardess they will be from January 2019) but in Economy they are still comfortable and the same service is received.
As I am 6'7" I always have to pay for exit row seats so the legroom wasn't an issue. The entertainment system is the same as is the food & beverage.
There are no premium economy seats and the Upper Class are very old Business class seats and I believe that is where the biggest issue will be as it is not up to standard, or even close.
However in economy you don't really notice much apart from different colour scheme and German being the prominent language in the toilets. The one negative I would add is that there was no prior notification of the change of aircraft. Would this had caused us to change our plans? No. If I had booked Upper Class - definitely.
Will I travel with them again - absolutely! I have to say the crew did brilliantly to deal with the petty complaints they encountered.