I am currently creating an entire new help section on my site, writing out every feature in text form, including a short video showing that feature described.
It is specific to my forum, so it wouldn't suit another forum. It contains what mods and changes are applicable to my domain, it refers to the site domain, etc. Not something I would ever try to write generically... Xenforo already have that on this site under their help section: http://xenforo.com/help/
Most my members are web savvy people (I run webmaster/admin forums, they should be), but, if you feel like this would help your members, then by all means do it. I would provide them with such a video, if I felt it's needed.