Is the web Document server really slow or should it load a document much faster?

I am testing this out in 12.1.1 but it seems spotty and not very fast. Also, on my tablet in desktop mode it doesn't work at all. I am assuming that is the correct behavior but couldn't that feature auto detect an unsupported platform and disable it? When I tried to use it, it caused my device to freeze up.

Has anyone got some insight as to help improve speed and reliability?