When I bought a Surface Pro I romantically imagined drawing directly to the screen as I traveled; drinking in cafes by the Seine, jet-setting through airports and all that. And, this will be feasible eventually, digital sketching turns out to be just as much hard work as any other way of drawing. Just a little less messy.
Working in a new medium is always a mix of lovely and awful. I’ve been taking the tablet to a weekly drawing portrait group I attend for a couple of months now. While still mild torture (I miss you charcoal) the processing is slowly becoming fun-ish.
After much practicing with different programmes, I settled on Autodesk’s Sketchbook as having the best interface for drawing live. Photoshop is just too fiddly for quick brush changes and such with out a keyboard, and Sketchbook lets you work in layers (so an under sketch to paint over is possible), as well as having a interface easy to manage with just a pen, a nice selection of so-called natural media brushes available anda fair amount of control over how they perform.
Here’s a couple of examples, each about 1 1/2 hours drawing time, from live models.
A Little Art 