IF you got x-plane 9.00 BETA, then you do NOT need buy version 9.00 final... if you just run the updater, then it will UPDATE your beta TO the final version.. there is no need to make another purchase.The key equation here is:
BUT, if you WANT to have the FINAL version on DVD for backup purposes, or to get the latest DVD INSTALLER, then you should re- purchase x-plane 9.00 now... though i do not recommend or suggest that at all... you just CAN, if you want the FINAL, NOT BETA, on DVD
Beta DVD + Web Updates = Final SimEverything that has changed from the beta DVD to the final DVD is available for free using the updater. If you want to buy more DVDs, Austin's not going to stop you, it's a free country. But we made sure that everything that was big and couldn't be downloaded would be there on the beta 1 DVD so that users could buy the beta DVD and have a complete sim.
So if you have a beta DVD, just use the updater to get the latest version (and RC3 is final, so if you have RC3, you're already done) and you're all set.
(Am I beating this to death? Yes...but...people get very angry at the idea that their DVDs are "not the latest" - so we put a lot of effort into making sure that you can buy the DVD early on and still have the latest!)