Been twice before, can't go this year though due to a holiday. Definitely worth it, just make sure you see all the flying displays and get round as many of the statics as possible to get your money's worth. Even though there's a lot on show this year, it's still quite a steep price. What should be great is the 44 (yes, you read correctly) flying Royal Navy aircraft taking place not to mention numerous others including the Vulcan. I managed to go with cadets a few years ago on the press day which was almost even better; all the same aircraft but without the crowds. Have a look over at this forum for all the latest gossip and news about RIAT...
http://forums.airshows.co.uk/viewforum.php?f=19
Last word of advice, pray it doesn't rain!