My Take
My students really enjoy creating Vokis. I think the educational value is best determined by the parameters in which students are given. Sometimes they just are downright silly, but when given specific parameters (topic, expectations of learning to include, etc.) they soar. The one big down side is that we've hadWe've difficulty recording our voices using our netbooks. We've had greater success with typing in the monologue.
How I Use It
I've had students use it to create movies for their peers teaching what they've learned about Texas Indians, scientific concepts, application of dialogue, and more. The more specific I am on what the final product should involve, they more focused my students seem to be. For example, when asked to compare and contrast two groups of Texas Indians, students chose from five groups and narrow to just two. Then, the Voki focused comparing similar and different specific elements of the two very well. Other Vokis during their free time at home have been fun, but silly. I figure that a little play with it helps in the academic setting because they'll better understand how to use the tools.