I was one of the doubters, pointing out the jarring experience from mixing the Modern UI and "tablet"-style apps with the traditional desktop interface familiar to previous Windows users. Modern seemed like an alien extra feature tacked onto the upgraded desktop experience. A feature meant to be minimized, turned off, set to "do not launch at start". Impossible to do that though; click here, click there, and all of a sudden you're inside a Modern app wondering where to point your mouse to get back to the desktop.
You know why I didn't like it? I was using it wrong.
Recently I got a Surface Pro. After 15 minutes of messing around with it, I was swiping left, right, up, down, and docking Modern apps with desktop apps (yes, even on the 10.6 inch screen). After 30 minutes I was seamlessly utilizing the mouse, keyboard, and touch to engage with the computer, and I wasn't consciously thinking about which tool (or hand) would bring about the next interaction.
Using a touchscreen transformed the Windows 8 experience from an "okay, it's fine" feeling into an sensation that I was really connecting with what's on the screen.
I wonder, what if Microsoft had required a touchscreen for Windows 8? While initial sales would have been slower, would satisfaction have been dramatically higher--possibly spurring a boom in both Windows 8 sales as well as a booster effect for hardware?
Think of how new games help drive hardware sales as people upgrade their video cards, processors, and memory--with Windows 8, this would be at a massive scale.
Since familiarizing myself with the touchscreen, I've discovered a few features that weren't readily apparent when using just a keyboard and mouse. At my desktop with a non-touch monitor configuration, I've been able to enjoy Windows 8 more because of these new features, but I can't wait to get a touchscreen desktop monitor for the much more intuitive gestures rather than clunky mouse movements.
What Microsoft should have told us all is: "If you're not using Windows 8 with a touchscreen, then you're doing it wrong."