Not a lot I can write about this one, because all the marvellous things on this we need to explore our place of work has blocked them. So unless I download them on the pc at home I can't really comment. On the face of it though they seem a very good tool.
Actually showing a small video clip of how you do things on the computer is very useful as some people can't grasp what you are telling them just with words. I have seen the small training videos on EBSCO the site that manages journal issues. They are quite comprehensive and if you don't get it the first time you can replay the clip.
While I can see this sort of thing being useful in training sessions I would have thought it would be just as easy for the trainer to do 'live' what he teaching the class. Obviously distance learning is another matter and it would come in very useful.