I occasionally consider switching from iPad due to features I would really like that are available on Android and Windows (specifically, multiuser support, active digitisers, sd card support). Both platforms would meet my basic app needs (social media, music apps, movie apps, etc) and have the benefit of lower cost. But one thing that I feel I might really miss if I left iPad is the quality of educational/reference apps that are relevant to adults (e.g. iTunes U, Khan Academy, Essential Anatomy 2, Brian Cox's Wonders of the Universe, The Elements) Given that I highly value these type of apps, I'm pretty sure Windows tablets should be disregarded at the moment. But what about Android? How good is Android with respect to these type of apps?