Catching the attention of our Anzwix system yesterday were "fast tile rendering" patches having reached LibreOffice Git. This work on LibreOfficeKit (LOK) provides fast tile-based rendering for text, graphics and buttons, and cell editing.
Unfortunately I couldn't find any solid data as a result of this work besides "rendering of text is super fast." These LibreOffice improvements were made by Ashod Nakashian. With LibreOffice 5.2 having already been branched, this faster rendering is presumably coming for LibreOffice 5.3.