Great article! will-change is simply a paradox.
I once wrote up a little piece about will-change and I came to the point that will-change is a CSS property which can’t be used efficiently (especially on mobile devices) without using JS to assign and remove it afterwards (touchstart, touchend,…).
Nevertheless I made some testings on Chrome and documented the facts concerning the browser handling and performance in an article (sorry, it’s german. Maybe the translator might help): http://webkrauts.de/artikel/2014/will-change-und-der-compositor-layer.
It’s on the one hand helpful for not recalculating and repainting the whole page, on the other hand hazardous if not tested, that the element on which will-change has been assigned is pushed into a new rendering layer, producing its own stacking context (like an positioned element).
I use will-change whenever it appears useful anyway.