I've used Google Docs a lot for taking notes on managing my "home computer lab." It fell down when I tried to copy commands I typed into a command shell and then copied/pasted into a Google document and then pasted back into the command shell. There was invisible reformatting that broke this in non-obvious ways. .Two consecutive spaces were converted to something that looked like spaces in the terminal but were not interpreted as such by the shell
I've been using Mkdocs since which uses Markdown and that preserves text perfectly. The formatting is lacking a bit but I can put up with that for the benefit of knowing when I copy a command from a document to a command shell (and often running as root) it is going to be exactly the same as what I originally typed.
The major downside to me is lack of standardization. Things don;t always look the same depending on which Markdown renderer I'm using (editor built in, Github, Makocs etc.)