All that was demo'd was the touch optimised UI designed for slates, tablets and other touch screen devices with a quick flash of what looked like a slightly updated "traditional" UI.
Yes the Metro look UI seems to work with a mouse and keyboard as well as touch, but if your sole choice of OS is based on how pretty the UI looks then this is a wasted discussion. May as well install Rainmeter and the Omnio Skin on W7 (which actually looks fairly similar, is preety good and has been around for 6 months or more
).
Baring support for ARM and cues around HTML5/Javascript for dev into the new touch UI there was practically nothing mentioned about any other change to Windows 8 whatso ever. It'd be like having looked at the Windows 7 UI a year before it was released and saying "Jeeze that crap looks just like Vista, they've done nothing but change the start button and wallpaper, i'll pass".
Although the UI look and feel is interesting it's not really the reason to upgrade a UI, hopefully you spend most of your time in Apps, not the OS UI. For me, at least the value will be the improvements under the covers, much like the step from XP to Vista to W7. Once you get past the UI changes (and remember, people hated the XP luna UI when it was first announced calling it "fisher price computing") it's speed, stability, security, support, dev API stuff that's the real deal.
I like the Metro interface for WP7 and I think it could work really well on the desktop. It's not a huge step from the W7 Media Centre UI which supports touch and keyboard/mouse with no problems in terms of being big and for me the Media Centre UI is really nicely done although often forgotten about.. The new UI will work well for touch, but, for a desktop or gaming PC it's the "other stuff" that will be interesting.