Is Surface a niche product?
One of the biggest takeaways from the presentation for me, though I haven't seen it mentioned in any tech blog writeups, was that Microsoft will only be offering the Surface hardware in Microsoft Stores and "select" online retailers. That means you won't be able to walk into Best Buy and buy one, which is exactly the kind of limited visibility that killed the Nexus One a few years ago.
I suspect that Microsoft is limiting the distribution of Surface intentionally to avoid annoying their hardware partners. People who aren't "in the know" will just go to Best Buy and purchase whatever Asus or Samsung hardware they see there, while sales of the Surface will be limited largely to Microsoft enthusiasts who know how to get their hands on one and are willing to buy it sight unseen.