We use Amex Platinum which gives us one free domestic return Virgin flight per year. In January the four of us flew from Perth to Hobart for a holiday and paid $0 dollars for the flights other than a small amount of fees - can't remember how much but it was bugger all.
The "secret" is to not book the tickets using Amex but to convert the points to Virgins Velocity FF points which gives you more flight km's per point than Amex. It took us about a 2 years to get enough points to get the 3 extra tickets plus the free annual one. An Amex Platinum card has quite a hefty annual fee attached but we are fortunate that we only pay $80 per year because we still have the old green Amex that the wife had when she was working full time so they don't charge for the Platinum card

You just have to be aware of the best way to use your points and you can get some reasonable value without going overboard by trying to put everything on the card.