I'm a 3d artist and concept artist who work with Sketchbook, Photoshop, Maya, ZBrush, 3DSMax, Unity, Illustrator etc.
I've been drooling over the idea of a tablet as a laptop replacement for months now, and patiently waited for the Companion 2 to come out, and now for any word of the Surface Pro 4. I've been leaning strongly towards the Surface over the Companion lately, but after properly looking into this matter of the buttons I have to say I'm deeply shocked.
A pen without map-able buttons is to an artist what a bicycle with no pedals is to a professional cyclist. You can still use it (sort of), but why would you?
The need for customizable pen buttons is so fundamental to an artist that I fail to comprehend how this could have been neglected. Seeing that this "Surface Hub" app thing still doesn't seem to support proper pen customization I can only assume that Microsoft does not care about the artist in regards to the surface and that we are not a valued audience.
I might hold out to see what the Surface pro 4 brings, but this will be the first thing I'll look out for.