We've used it three times now and would highly recommend it - well worth the money. The cost is similar to a cooked breakfast at one of the outlets in the airport. We always go Saturdays during school holidays so it is busy but we've always found a table.
In theory you have a quicker route through security but we've never used it.
You can enter the Vroom 3 hours before departure (we always get to security about 4 hours before so that we can do some shopping before heading up there.)
The tables are in two sections - one bar area for adults only (no good to us I'm afraid

) and a family area.
There is a buffet breakfast with cold items (fruit, pastries, croissants, chocolate brownies, cereals etc at the time we are there for a 11.30 ish flight). A hot buffet which you can only have one of the menu per visit but unlimited visits (cooked breakfast and toast) and a hot drinks area plus an area for little children (not applicable to us anymore.)
There is an indoor play area with soft play toys for toddlers.
Then there is a room with about 6 computers for internet use and a table football game and wii or similar game (we never have a problem getting computer access but lots of issue getting any access to the others).
The toilets are clean, there are Virgin staff at a booking desk (which we've never used) and complimentary papers and magazines.
Finally it has a terrific view of the runway and you can watch the planes come and go to your hearts content until your boarding is called.
Major negative not booking to go with virgin holidays for us is that we can't do this.