I've done the "half priced tickets" deal before and it isn't worth it. You spend 2-4 hours waiting in a line during your vacation for tickets that may or may not be there, and it's 50% off the retail price. You can often find discount codes online that will still save you a decent amount and allow you to actually do stuff during the day--if you book your tickets in advance. The tickets I purchased from them ended up being about the same price as a promotion they were having at the box office!

If the VIP line thing works and you can't find any discount promotions online, sounds like it might be worth a look.