This is in a mid-size document that is meant to be lecture notes for a math class. Admittedly, this is formula-heavy, but it is far from the complexity of a PhD thesis.
In addition to having to wait 5-7 seconds to type a formula, the document scrolls away from where I was, and the formula window appears just at the top of the view, so I can't see the formula being rendered.
A small thing, but kind of defeats the purpose of easy wysiwyg outlining.
This happens on a 1 year old Mac laptop running MacOS 10.12.6 (Sierra).