I fly VS a reasonable amount and the issue I think is that they are very inconsistent. Some crews are really good and someone are really very poor.
I'd recommend a look at the excellent V-Flyer site (v-flyer.com) and read some of the trip reports. These are generally written by people who travel a lot, fly Virgin regularly and like the brand. However, read a few of those and you'll see that consistency isn't Virgin's strong suit.
I have heard say that (even by airline standards) the cabin crew aren't well paid. What is true is that if you get either an unhappy crew, or a group that are way to focused on social interaction with each other than on looking after the passengers it's going to be a bleak experience.
All in all Virgin is a mixed experience. In the air, even in Upper, the food is pretty poor. But other things, like the Clubhouse and the Upper Class Security facility really do set the airline apart.