Both.
I find it useful when I use them in posts. For example, I can easily ask “Have you tried safe mode?” and there is no need to manually add the link which explains what safe-mode is and how to use it. Though I would sometimes prefer a template, because I tend to write “safe-mode” and at the moment I have to use the preview to check whether I used the correct spelling. So I could suggest adding safe-mode but I like that I can reduce the number of links by using a different spelling.
This leads me to:
It gets on my nerves when I read documentation, like:
It distracts me while reading. There are a lot of links which were probably all added because of autolinking. But I still feel the need to check whether they really are. It could be that some of them were added intentionally, linking to something else.
That’s why it sometimes disturbs my reading flow. But this could be solved by limiting the number of times a watched word is linked or restricting auto-linking to e.g. “data explorer plugin”.