I am an architect so more than a little biased. I use it everyday, OneNote for ideas and notes, Drawboard to sketch over plans or mark up material, and Sketchbook or Mischief to relax. Everyone should color http://m.huffpost.com/us/entry/7088048
Freshpaint is great but no layers. Autodesk sketchbook is great but you have to pay for features yearly or buy Sketchbook Pro 7 outright. I am trying a new one Mischief that is really interesting