In the age of YouTube, screencasting and video tutorials are now a viable replacement for traditional software documentation.
From a user perspective, watching a series of ten minute screencast tutorials is a preferable, often more effective method of learning how to get to grips with a product, than reading a user manual could ever be.
From an SEO perspective, screencasting is an effective method of increasing awareness of a product online: the same content can be shared with multiple video sharing sites, and YouTube results are prioritized in Google, so a high quality screencast with careful keyword research can be marketing dynamite, as well as helpful for users.
I have been producing screencasts for ten years and have wide-ranging experience with the popular screencasting tools on the market. Video tutorials can effectively complement - and sometimes replace entirely - traditional documentation, if approached correctly.
I would be more than happy to discuss the best approach for your individual needs.