Jason Kottke, at Kottke.org:
Set aside for now that Surface does look genuinely interesting, that the price hasn't been set, and the thing isn't even out yet. For a piece of portable networking technology like a smartphone or tablet to be successful on the scale at which Apple operates, you need to have an ecosystem, a network of interacting devices, software, products, and services that work together...hardware + software is not enough. Apple, Google (and partners), Amazon, and possibly Microsoft are the only companies with the expertise and pockets deep enough to build their own ecosystems. Ok, maybe Facebook in a couple years or if Nokia can dig themselves out of their current hole, but that's really about it. Jason Kottke lays out all of the things Microsoft needs to do to make the surface successful, if their goal is to directly compete with the iPad.