I have an Asus convertable tablet that is more than 4 years old now but it still works great with Windows 7. I use it every day on my train commute to work on VS projects. I also use it with OneNote to sketch out ideas related to programming (visualizing collision detection for my 3D game engine, making framework diagrams, etc), as well as all sorts of other drawing related purposes. I can't use an iPad like that (in spite of there being aftermarket "styluses (styli?)" for it that doesn't function nearly as well as an RF stylus since they need to simulate a fingertip and all have fat tips).
I really do hope that whatever MS comes up with for their "Immersive Tablet UI", retains stylus support. Traditional Windows tablets didn't fail because of stylus support, it failed because it had a $500 - $600 price premium and there just weren't enough stylus-only apps that justified such a price premium. I believe there is a whole category of applications that would be very popular to use with a stylus if the hardware is cheap enough and good enough to become popular. If the iPad had true stylus support, I think there would have been a lot of apps that took advantage of that (why would there be an iPad-stylus aftermarket if there wasn't any demand?). MS could have an advantage over the iPad if they create a dumbed-down and easy to use tablet like the iPad but still gave it pen support.
In addition, I think it is time MS creates their own tablet hardware. Going through OEMs only dilutes the "vision" MS has for a tablet. MS should still license the OS to any OEM that wants it, but with a true "reference" MS tablet out there, they will no longer be able to release sub-par hardware and think they can compete. And with the current low marketshare of Windows tablets, I don't see why this could trigger antitrust issues. Apple is clearly dominating this market right now, and everyone is fine with them having a much more closed tablet than MS would ever have.