It's a crazy concept. When I visited Thorpe loads I didn't feel the need to buy Fastrack because if I didn't get on something I knew I could the next time. You work out when are good times to visit as well. Also, I'd have to visit with someone else with the VIP pass or the Fastrack perk would be wasted.
I guess people are buying it though. Unlimited Fastrack or a trip to Europa? Hmm.