Screencasting is a great way to teach, demonstrate or document online activities. People that are interested in e-learning, information design, education or those of us that need to show folks how to do some have all benefited from screencasting software.
I know I have. I have used it to help remind folks how to perform a certain computer task. This was after I explained how to open their e-mail program four times and it didn't stick.
TechSmith has a series of videos called The Forge. Sometimes there are demos and reviews. Chris McQueen handles that part of the series. Matt Smith interviews people that are in the business of using screencasting professionally.
This is a wide range of users so you can be exposed to a range of techniques. There is a diverse community of information creators that want to create better instructional videos. This is a good step toward servicing that population.
Full Disclosure: I have purchased Camtasia and SnagIt. I have used other screen capture software but I do prefer these two products.