Just my thoughts:
Limiting it so you can only sell through there, and not your website or on your own is a bad deal; it also limits formats, etc. This is, IMHO, no good.
In regards to the claim "find me somewhere else that lets you keep 70% of the revenue" In this one, single instance.. that is a problem in and of itself. Many of these book publishers (specifically texts) receive compensatory funding from states and they receive special tax incentives, etc. So, let's say you say "well, it's all apple ipad, and now the author keeps 70%" Wait.. the author isn't the one who should be getting 70%. In the case of a university, many universities have clauses that dictate some of that needs to flow to them; in the case of a compiled book, like a general studies text, some of that funding is underwritten by a co-op to manage the research/etc.
Suddenly saying "we're going direct" is like telling Universities and states to go jump in a lake with the tax revenue they've pumped in ;) I'm not sure how they will feel about that.
I admit, I'm someone who kept almost every one of my college texts. I sold a few, but a large number I kept. I can't imagine keeping six years worth of texts in an iPad or in any format.. it's not like a class has "one" text; several classes I was in, especially historical and literary, had numerous.
It's the direction this is going, but having some sort of sell-through and content delivery exclusivity seems like a very bad deal for the taxpayers who invested in the development and support of the university profs/etc. who are providing.