I can't see Win8 tablets failing.
We will see all the traveling business people carrying these Win8 tablets vs a laptop.
This is what I did when I was hopping around Afghanistan while contracting, my company gave me a laptop with a 15-16" display and an extended battery; they refused to give me a smaller laptop. I HATED carrying it around due to its size and weight, and was always having to deal with people around the office "borrowing" my power brick for their laptops.
I bought the Asus P121 and never looked back, my laptop sat in my storage trunk for the rest of my time out there. There was something about being able to mark up a chart/powerpoint/map right there in front of people like it was a little white board, I got a lot of impressed looks from people whenever I pulled out the stylus and started to draw up changes/ideas right on the spot.
Now that I'm back home, I still use my tablet very heavily for meetings and walking around the office. It's running Windows CP 1 on it at the moment, so there are a few glitches here and there; but, I've given a few presentations on it using the HDMI out and I still get people saying things like "cool!" when I mark up something. Don't get me wrong, I do 90% of my work at my desk with my full-sized KB/Mouse and Dual Monitors. But when I'm not at my desk I have my tablet at my side at all times, I just like being able to walk into someone's office and have something that I can do actual work on.
To sum up, having something that bridges the gap between desktop computer and a smart phone that has Onenote, Office, and the ability to most of what a desktop can do (because it's running the same OS) all in a small package is just awesome. And Microsoft doesn't care if their device fails because some other company makes something better, they make money on licensing regardless. I think that MS has a real shot of balancing the scales between them and Apple if they can truly make Win8/RT and Windows Phone into a more unified platform (apps that run on all three Operation Systems).
I'm looking forward to seeing if MS can actually pull this off or, at the very least, make sure apple doesn't rest on their success.