Re: The person who writes documentation
You write documentation for someone who doesn't know the product.
No: you need different levels of documentation, even experienced users need documentation - but about things that would mystify a novice user.
Yes: you need good documentation for the new user that assumes that they know zilch; this will let them get it installed & running. I have wanted to try out several packages and given up because I could not get a basic installation to work. Optimisation & customisation happens next.
Also: many programs produce hopeless error & information messages, eg not saying the name of which file is missing, or just the name but not the directory that it is in.