That's interesting. Did you update via the OTA updater or Odin?
Let give a more precise description of this weird phenomenon:
While using S Note or Sketchbook in Portrait I can draw smoothly when I immediatly bring the pen in contact with the screen, so long as I draw a continuous line.
However, as soon as I let go and the pen cursor floats around for about a few seconds, pen input and cursor start lagging.
If I remove the pen from the display (cursor no longer visable) and put it back on (direct without delay) than I can draw smoothly until I start a new line.