Been using OSX since Cheetah/Puma/Jaguar/Panther and Tiger and now Leopard since Beta stage during WWDC and officially bought it a week ago. My personal view after using it :

This OSX 10.5 getting improved with a little noticeably changes i.e : TimeMachine, Spaces, 3D dock with "Stack" function, PhotoBooth with Video recording function, the rest just minor changes which are not important for me. 300 features? -ahak just a hype I supposed as it still the same like TIGER. My verdict : For RM509 not that worth it. if you got extra money just upgrade it otherwise just KIV your intention. BTW, I would iterate that THIS IS JUST MY PERSONAL VIEW.