A quirk that I get with my Bamboo Fun Pen and Touch tablet and Photoshop CS6.
I have the tablet sensitivity on, but at times when I want to get into detailed strokes the sensitivity sort of "Turns off". If you take a look at the picture, the nice and creamy strokes are when I flick the stylus across the pad. The dark circular strokes is when I pull the pen across slowly. This is the same brush. This makes drawing details pretty darn hard, and it just started doing this. Freaking sucks.
I use the same tablet with Corel Painter 12 and this problem doesn't exist, Tablet PC Input Service is also turned off by the way.