Although I haven't seen one yet, based off the reviews I have read, it seems to be an overall decent machine.
Many reviews touched on the friction hinge used by the Surface, however only one review by Arstechnica (out of Engadget, The Verge) touched on the 'lapability' of the machine. And it's true, when I am using my laptop, sometimes I use it on one leg or when I have both legs arched. In those situations, the Surface would fail as a laptop. That wouldn't necessarily be a problem if it was marketed as a tablet, but since Microsoft is marketing it towards Mac Air people, the Surface kind of fails in that regards. Only Ars mentioned that point adequately. I was a little disappointed in the Verge's review.
And one other issue is when the reviewers and Microsoft are touting the lightweight aspect of it relative to the Mac Air. But they fail to account for the weight of the keyboard cover of the Surface. Sure, even with the cover, the Surface is lighter than the Mac Air, but they should still account for it in their weight measurements.
That is all.