Been using this for over a decade, back when it was called sharelatex. Always liked it for the free cloud storage, nowadays mostly just use it when I need to update my resume.
I've used Overleaf before the ShareLaTex merge strictly for the collaboration feature - setting up and using LaTeX on Ubuntu was easy enough, especially since pdflatex (just tex -> PDF, no more tex -> DVI -> PostScript -> PDF nonsense!) and me or a collaborator usually compiled the final PDF locally IIRC.