I have been doing training videos for many years on web development and office products and they have done very well, although that area has a tremendous amount of competition.
Videos work really well for any type of training as most people find it easier to learn while watching someone else complete the task. It is also much quicker to learn that way than from reading text. Although I need to point out that the quality of the video and audio makes a huge difference on how well the videos will do on the web.
There are a lot of videos out there, with bad information, poor video quality and poor audio quality that really hurt what the contributor is trying to say. Like everything else we do in life, take you time, pass along good and accurate information, and work through the video with a third party person to make certain that nothing was overlooked.
We get so used to doing things in a particular way, that many things we take for granted when creating a video may not be obvious to a viewer. Have someone that is not that familiar with the subject go through the video and perform the steps prior to publishing. You will be surprised at how often what you think is a simple common sense step, may not be so simple to someone not familiar with the topic.
Just some thoughts.