I have been working my way through the Plymouth University's iOS Development in Swift course on iTunes U over the last few weeks. The ease of access to the materials has meant that I can squeeze a course section or two into my lunch break. While this is down to how the course is presented by the instructor, iTunes U has provided the platform.
Bite sized learning like this may not be the most effective or efficient way of learning. For me though, it has shown that I am willing to put in the time and effort. My advice, if you are interested in learning a new skill, check out iTunes U first and see how you get on before splashing out on a paid course.