Side Note:
If you want to download a couple videos or course material from iTunes U, the iTunes app works fine. However; if you want to subscribe to one of the iTunes U courses or collections, download and use the iTunes U app. It does a better job of keeping the collections organized, and you must use it for the courses.
Apple should probably complete the separation by removing the iTunes U store from the iTunes app; or at least add a pop up warning when you attempt to subscribe letting you you know you need the iTunes U app.
It's a bit confusing right now.