The Dropbox guide designed by Ueno sort of mimics the feel of a printed manual. I like how it is more like a quick start guide that also has links to other support articles. That way you can still get the help you need without having to include everything in the guides.
Ueno won a few awards for the design. I agree that it’s easy to use and works well on desktop and mobile.
I also like the feedback buttons at the bottom of each article so they know what is working and what isn’t.