The courses are definitely worth doing, but the issue with free courses is it is very hard to get motivated. You will learn very little watching the videos. You will learn by spending many, many hours doing exercises and coding (for a programming course).
In a real university course that costs lots of real money, you will have nights you miss out on sleep in a desperate attempt to get an assignment completed on time. With free courses, it is hard enough to just stay awake, let alone work hard.
So if you want to seriously do a course, I think you need plan to keep you motivated before you even start. Do the course with friends. Have a programming idea with a deadline that you work on while doing the course. If you pick a course like Programming for the iPad, have a real project planned before you start, and set yourself a deadline for a date to submit the App to Apple for approval. It does not matter if the final App is not brilliant. It matters that you complete it, so that next time you can do it better.
If there is no plan, you will discover that there is nothing more boring then watching 30 hours of someone talking about programming (or whatever else the course is about).
Richard.