For the customers: Do you actually read through script manuals? What are things often missed? What's great that some do? For the developers: Do you have a manual? Why or why not? For those that do, did you create it yourself or have a third party create it?
I'm a customer and yes I always read through script manuals for installation instructions because I'm not techy at all. I love it when there are detailed screenshots, and I hate it when they just breeze past some details that the average marketer like me wouldn't know about.
We rarely use 3rd party scripts and when we do it tends to be components either like the PayPal API or a URL rewriter. We will read the "manual" - though for components the manuals tend to be on the light side. Our own applications are not for public consumption and we retain the copyright to them and as such we create a "user" manual but not an integration manual as if anyone did try to do this it would mean they are almost certainly breaching our copyright.