I wonder if it's gotten better since 2002-2004, which is when I used it a lot.
I'd be curious to hear what you think about the equation editor in Desmos[1] (full disclosure, my employer).
We use an open source WYSIWYG typesetting library called MathQuill[2]. The keystrokes you use are very similar to AsciiMath, but the result is direct editing of the typeset math. E.g. you type '_' to move into a subscript, '^' to move into a superscript, '/' to create a fraction, 'sqrt' to create a radical, etc.
I believe that I can edit much faster with this interface than with Microsoft Equation Editor, and that it's approximately similar difficulty to learn. But I'm biased.