Both the Surface Pro and Surface RT have a built-in kickstand made of the same sturdy VaporMg material that encases the tablet. It's great for desktop use, but awkward and unstable on your lap. By comparison, a conventional laptop with a hinged screen balances much better on your lap or knees.
Another limitation of the kickstand: viewing angles. A laptop display can be positioned at myriad angles for optimum viewability. The Surface tablets are far more limited in that regard -- a shortcoming that limits their laptop-replacement appeal.