I've still got snow leopard and it won't let me download it unless I have Lion. I'm thinking it might be worth the upgrade, though.
It's a great app.
Nice walkthrough.The interface is very similar to Apple Pages - so I guess, if you are familiar with that it should be very easy to use.This app opens up a lot of opportunities in the education world.
Could you publish your title for ibooks, then change it around and republish it on Amazon or somewhere else. Same basic content, just titled a little different for the apple version, maybe add in some extra content. This way you could have wider distribution of your content but not be so stuck in one channel.