I think most people who have been commenting on this policy don't fully understand it. It only applies to in-app purchases. Exactly the same content can be payed for externally - and then viewed on the iPad - and 0% will go to Apple. They are only raking in the 30% when people use the convenience of in-app purchases. 30% might well be a bit heavy but it is Apple's prerogative to charge what they deem appropriate for this convenience. It is fair in a sense because if Apple is bringing in new subscribers who have found a publication via the AppStore then of course they deserve a cut. But existing subscribers can carry on paying monthly or whatever on their credit cards/direct debit and then Apple will take zero cut.
It makes sense. Why shouldn't the content providers pay some form of fee?
They are instantly getting easy access to over 130 million potential buyers (not counting in the newly opened desktop App Store).