I owned an iPad 2 since its launch, about three months ago someone broke into my house and stole it (among other things.) I decided it was time to go shopping, and finally settled on a first generation Surface Pro.
After using it for three months, I can say I prefer it over my laptop *and* my iPad. When I want to develop software, I switch to the desktop and plug in an external monitor (which means I get a second 10-inch screen to load documentation or whatever.) When I want to browse casually, I just unplug it from the extra monitor and go mobile. I don't like the screen aspect ratio (too tall and skinny in portrait) and the battery life needs work. It's also a bit heavy, and the app store isn't as rich.
Still, it has been incredibly nice to have access to my desktop and tablet all in one package. As a desktop, it's actually pretty solid. I don't do heavy media editing (most of my software development involves financial accounts) so it hasn't so much as hiccuped with what I've thrown at it. Now, I don't feel like the Surface Pro is better than an iPad as a tablet, though it's a solid desktop and a decent tablet. Still, having my desktop in such a small form factor has been a dream.
It feels like the natural progression if technology. When someone gets the hybrid-OS to work right, I could see desktops, laptops, phones, and tablets all becoming the same product in a way.