I really like the Behaviour, Speed, Ease and nice erasability of the Blob Brush. There's only ONE thing that would need to change for it to be perfect: the way strokes are previewed when drawing before letting go of the stylus.
Personally i often just do the Adam Phillips (Brackenwood fame) method of a vector rough brush and take a red or a blue color and make it transparent. With that i can "build" my drawings a bit more. The Freehand tool does this very nice however the Blob Brush previews strokes much more opaque until you let go. This doesn't seem like a big deal probably but for a nice sketching experience it really would help to have the Blob Brush Preview it's stroke a bit more nicely like the Freehand.
A Gif to illustrate what i mean better both have the same color and opacity settings:

Hope this makes sense and thanks ^^