Between coming up with a curriculum, teaching, assigning homework, and getting important info to students, teachers have it rough. The iTunes U app is going to let them do all of that from an iPad. Which means students can basically take entire courses from their tablets.
Using iTunes U, teachers can stream lectures to all of their students, regardless of where they are. They can also be downloaded later if they're too busy streaking the quad. Professors can post assignments for their students, field questions as they come in, and get important messages out. It'll never be as good as learning in a room surrounded by your peers, but it's a good alternative for students who can't be there for whatever reason, or for online coursework. Plus, you if you missed what your professor said, you can just rewind and check it again. Organizing you stuff and referring to notes should be easier too, since it has keep integration with the new iBooks 2 notes.
Six universities including Duke, Stanford, Yale, MIT, The Open University, and HACC have already adopted this, and K through 12 can now sign up as well, which is huge. iTunes U currently has over 100 complete courses already, and it would be prudent to expect that number to skyrocket in the very near future as adoption grows. On the downside, playing sick now means you still have to go to school. The iTunes U app is now available for the iPad and iPhone.