You really nailed it with that first sentence. I can't tell you how many times I've done custom layout operations with absolute positioning that should be slow because they're being executed entirely in JS, but are much faster than the built-in layout operations. A good case in point is YouTube and its fixed header and left-hand menu: IE11 and Edge both have real problems with these fixed elements bouncing when scrolling down on the page. This is a trivial thing to implement without any visual artifacts when using absolute positioning.
