I'm BA crew and have also flown Virgin - 3 times.
Once LHR-ORD, crew and service excellent.
Once SYD-HKG, crew and service excellent.
Once HKG-LHR, service good, crew obviously tired and not at their best.
I'd have no hesitation in flying them again; I think, like BA, the overall service really depends on the crew you get on the day.
Unlike other airlines, they're not robots but human. If they're not in a good mood, it might be reflected to some extent on the service provided. That's not an excuse, just the way some crew are.
Virgin crew are generally quite young, and without wanting to open a can of worms, I think this definitely has consequences (good and bad).