According to the article I read recently, apparantly Duke University gave their students iPods in order for the students to download educational lectures. By downloading these lectures, a student was able to listen to the lecture as many times as needed and learn and take notes at his/her own pace. The article also went on to state that the students who listened to these lectures actually performed better on the tests/quizzes on the lectures. The article can be found at: http://www.online-artikel.de/article/learning-podcast-for-students-at-the-university-16483-1.html
I believe that a student's ability to download lectures and listen to them at their own pace will be extremely helpful in improving grades. However, I feel that any teacher that uses this method should still make attendance required as some students may feel they can skip class since the lectures are available for download.