My mate just got back from the states (his first visit) and he bought the VIP Experience
I havent done it, so not talking from first hand experience - but he said it was definitely worth it, and if he was to go back, despite now having done it he would buy it again.
From what he mentioned you get: an extended backlot tour with a lot more stuff than the regular tour - see a few more sets, you get to go into the props room and actually touch and take photos with props from movies, you get driven around in buggy so not too much walking, you get a buffet lunch which was apparently very good, front of line access to all rides all day (no fastpass type time limit thing - just go to the front anytime you want) and 20% off all merchandise.
All up pretty good - i'd definitely do it next time i head over