We've upgraded with both cash a week prior and points upgrade at the Lounge counter. We were treated with impeccable service on the 737 each time. For the points upgrade, they politely advised that meals may not be first choice, but as the cabins were empty, we got whatever we wanted. The full cabin was probably the one with the least amount of attention but it's obvious why that was.
I hate that there would be a manifest with fare classes identified. Just because I didn't pay the $2400 J class fare, doesn't mean I didn't already spend $10,000 earning the points on my Virgin credit card or flying the thousands of paid miles on Virgin PE flights for my points in the first place. I think anyone who has secured a J fare is a J passenger.