It's been a long time since I've used the equation editor in Word. My prior experiences with it were none too pleasant. So I had some trepidation this time around. Most of that was unfounded. It worked as it should to produce integrals, fractions, exponents, simultaneous subscripts and superscripts, and the spacing of terms.
The one complaint that I have based on this use was for evaluating a definite integral. I'm used to notation which, after integrating the integrand, places a vertical bar and then the bounds for integration. I didn't see a way to produce that vertical bar with integration bounds. The vertical bar needs to be the same size as the integral symbol, which is much larger than the regular font. The vertical bar you can access on the keyboard isn't big enough. So I'd like to see Microsoft add that particular symbol to its set of tools.
I should also note that when the document converts to pdf, the math comes through fine. Here is an example, from what I produced earlier today.