They don't seem to be selling too fast as its quite a steep price which is only set to go up next year given this is an introductory price.
As for the whole experience with buying a V.I.P pass I'm a little disappointed in Merlin and how in my case my purchase was handled.
I phoned Wednesday at 6pm, took me 20 mins to get through, gave him all my details everything was sorted and we said our goodbyes. Never received a confirmation e-mail or the phone call back and the money was not deducted from my account (even as I write this message). It was only today when I was on the hotline did my post come and got a congratulatory letter from Merlin confirming my VIP pass. But I'm going Alton Towers tomorrow with my letter from Merlin in hopes I'll get in otherwise I'll be red faced, the phone call I'm expecting should give me further instructions on how to use my pass straight away until the packages are sent out next week.
As for the V.I.P experiences I have heard that for places like AT there may be some lift hill walks (smiler, blivvy maybe), not exactly exciting but its an experience most won't have so that is a nice little perk to have included.
I was at AT Thursday and a father and his family who bought 4 managed to get in and were each given an unlimited fast track wristband and they did 6 rides of The Smiler while people were waiting 100 mins
, that's why I bought mine.