I came across this article today about the importance of font to improve reading comprehension.  In the past four months, I have been doing a LOT of instructional design for the variety of classes my business now offers.  Much of this work is based on Sharon Bowman’s awesome, awesome book, Training from the Back of the Room, and one of the six trumps that is relevant regarding font selection for class material is below:

Different trumps the same

I have been mixing up fonts in my handouts because I felt if I used a standard font, it would be sightly inconsistent with the classroom experience I am trying to create.  In all my classes, I work to create a learning environment where peers are sharing experiences with another and interacting with the material.  The variety of fonts on a page were just another manifestation of my training philosophy.  Glad to hear it actually helps with retention.