I have the Surface Pro 3 and use Harmony 11 on it from time to time. It works great, and the touch gestures work nice as well. You can zoom and rotate the canvas by pinching and twisting your fingers.
And yes you get pen pressure on the N-trig. I had to set my smoothing higher on my brushes to get good lines though.
The interface and buttons are very small in Harmony on the SP3, mostly because Harmony isn’t optimized for the screen size. It’s workable, though I wouldn’t want to spend hours at it. I have a 21" cintiq at home for serious work in Harmony, so the SP3 is just if I need to be mobile.
Storyboard Pro works well too.
You’ll also need to have an external keyboard, or get comfortable with the keyboard attached at the bottom, as Harmony really needs the keyboard for any serious work.
Other apps work good. Manga Studio 5 is what I use constantly on the SP3 and it is awesome.
I have adobe CC so I have the optimized photoshop, and it works fine. Not sure about Cs6.
As for other programs i’m not so sure. You can check a blog called http://www.surfaceproartist.com and they have a running list of software working on the SP3.
A note about the fan: It gets loud. I wouldn’t recommend using it as an internet device because that kicks the fan on in high gear for some reason.