This is not a major issue, but noticeable nonetheless. I am interested in the technical details what could cause this behavior, and hopefully this could provide insights into how to fix it as well.
I noticed that the maximize window animation on my newly bought Dell XPS 15 9550 stutters. Nothing major, but the animation is far from smooth which is what I would expect from a high-end product. If I have to guess it is reduced to 10 fps or so. At first I thought possibly the graphics drivers were not installed correctly, but this was not the case. Most other animations are smooth, e.g., the start menu which pops up, action center, ... and even the minimize animation!
Subsequently I noticed that maximize animations on my secondary screen (which is only HD, not Ultra HD) ran smoothly. It is only windows which near about 3/4th of the full 4k size (3840x2160) which stutter when maximizing.
The graphics card used by Windows 10 is Intel HD Graphics 530. Given that they put this in a laptop with a 4k screen, I would expect they at least benchmarked it to see whether it runs smoothly for perfectly normal use. An exact same machine of a colleague of mine shows the same symptoms, thus I do not believe it to be a restricted issue to this single machine.