The V-Room is very worth it, for the peace & quiet & great views of the runway. It's a one-off charge which can be pre-booked if you have purchased your entire holiday from Virgin. It's also nice you can take care of any VISA documents in the lounge beforehand as they hand them out.
Free food & drink, video games for the kids & just relaxation.
IF like us you have just booked a flight with Virgin they won't let you pre-book the V-Room although speaking with a friend who works for the airline if you turn up on the day & they don't have a full rotation of bookings so long as you show your Virgin flight ticket they will likely let you in for the inflated on the door charge. It's just the company way of extracted a higher price for the service than allowing you to pre-book.
if you get the chance to go, go.