I updated my Lumia 640 LTE recently to WM10.
The process was hard reset->upgrade to WM10->hard reset->update to 10586.420.
The problem is, when I use my finger to scroll in certain apps(Store, MSN Weather, MSN News, Windows Feedback), I notice a strong stutter. It not just looks unsmooth, the screen jumps up and down, sometimes quiet pronounced. As soon as I lift my finger off the display, scrolling becomes smooth again.
Today I reported the problem via Windows Feedback. I also noticed other users experienced the problem
a while ago.