I haven't noticed any improvements in the scribbling. It's been like this right from the beginning, rather quick, but still with a short delay between when the pen hits the tablet and when the ink is actually displayed. No major issue.
I've never personally had the problem with the blind spot.
But I have two issues with scribble. First, there's two mysterious displacement lines, between the arrows marked 1/2 in the image. That gap/line is also occurring in pdf sketches, i.e. anywhere the pen is applied. Second, why is there tons of white space on top and bottom of the image (3)? Is that because of the blank template? (Larger resolution linked below the image).
http://www.georgruss.de/tmp/booxm90-scribble-large.jpg