This is one of the first structured "study" of the use of Skype in the classroom. Authors note that "[Compared to other systems], in Skype, typing is not an issue; learners can save all the mental effort to communicate thoughts, raise questions, and seek clarification by listening, thinking, and speaking. Skype users reported that talking made them stay on task and motivated them to learn." They also quote Skype as an alternative to much more expensive classroom systems.

I believe that today, Speechi Live, which is the online e-learning tool that fully integrates Skype is not only much cheaper, but also much better than those "expensive classroom systems".

Source