I've flown Virgin Atlantic close to about 50,000 miles in the last four years, and at this point I actually have mixed feelings about them. Here's what I like about them:
The goody bags are really cool- you get a rubber duck attached to your toothbrush
The entertainment systems are great...when they work (see dislikes section).
The staff and crew are always really great, in my opinion. I love the attitude that Virgin has as a whole. It makes you feel welcome onboard even in economy.
Their sense of design is great. A lot of airlines, especially domestic US airlines, seem to forget about overall aesthetic- Virgin certainly puts an emphasis on this, and I commend them for that.
And here's what I dislike about them:
The entertainment systems have been broken on about 40% of my flights- ranging from fully inoperative to just slightly malfunctioning.
The legroom is not very good. Especially having experienced AA's legroom recently, I really find it hard to get comfortably in their seats. But then again, it's not much worse than any other carrier really. So what can you do.
The A340s have felt a bit cramped to me. More so than the B744s. Nothing horrible, but it is a difference that I notice.
So there you go- hopefully this gives you an idea about what VS is like. Of course, my experiences with them may in no way be similar to yours. So this is just my opinion about them.
Overall, I have enjoyed flying with them, and would be happy to fly with them again if they were offering a good price. Their product, I think, succeeds, because they are unique in a way that many airlines shy away from these days.