I've got this on pen, too. It's not as obviously bad as the keyboard and touchpad lag but it's still pretty awkward.
It's really awkward. I write a full sentence without stopping and literally when I lift the pen off the screen, I'm just watching and waiting for the last half of the sentence to appear.
Sounds like it's the input queue in general that's the problem. I don't know if it's all controlled by the same thing, but it's interesting that every form of input is connected. Microsoft has to be able to fix this -- sure would be nice to get some feedback.