premium passes give you year round access to the Water Parks, what's left of PI, and DQ.
For us as a UK guest its about the same cost a a UK resident 3 week pass. So for us, its worth it just for a 2 week trip, the money you save on Dining, merchandise and parking makes the difference between a 3 week UK pass and a premium annual.
That and we normally spend at least 4-6 weeks a year in Orlando.
The best perk we find, is that you can enjoy the parks at a slower rate... Coz you not using one of your 4 days etc, you can just take it nice a slow, and take in the atmosphere of the park bit by bit.