Josef, Slawomir is right. For authoring mathematics: still a blackboard or sheet of paper rule:)))ASCII editors are not good tools for presenting or authoring mathematics, formalized or not.
I would agree with presenting, authoring is a different matter. The Mizar team even went from nonASCII-allowed to ASCII-only couple of years ago for purely practical reasons, and people got used very quickly to "in" instead of the \epsilon character.
But then someone has to create a special keyboard for writing maths;) These things would be great. So far auctex mode in emacs has to do the trick for me.
I think that this might change over time, e.g. with good Unicode tools (in this sense XSymbol is still ASCII, which is good).