One thing this Surface has, that the Air does not, is that touch-screen with a Wacom pen. That to me sounds like a strong selling point, at least to graphic artists. So many pressure-sensitive bluetooth pens are being made for the iPad, with varying success, but the Surface comes with the pen out of the box.
I'm reminded of all the tablet PCs that came before it. They had a stylus.
What's different today versus the decade of tablet PCs before?