Open source devs: please, please add screenshots...
I beg you, if you are a developer of an open source app or program - add screenshots of your app to the README file.
When looking for the perfect app, I had to install dozens of them just to see what the user interface looked like and whether it suits me.
This will allow users to decide if the app they choose will suit them...
Please, don't think about it, just do it....
I personally hate screenshots in technical documents. You can't copy and paste any text in a screenshot, you can't easily zoom in and often the resolution is not great.
It definitely depends on the context but please do not ever include screenshots of technical text instead of actual, useful plain text.