It actually works quite well with mouse and keyboard. If you can, try booting the consumer preview on another partition or something and give it a spin. It's free and doesn't take long to download. If you're using a laptop with a touchpad you can use the touchpad to make touch screen gestures such as swiping. Otherwise it's just as easy to navigate with a mouse. It actually makes Windows less of a jumbled mess. Everything is organized and looks sleek. It runs really fast as well. It boots faster than 7 (in my experience) and everything runs smoother in 8 than in 7.
Windows 8 most certainly does not work well with a mouse + keyboard, at least not nearly as well as its predecessors did.
case-and-point: a simple shutdown initiation
Windows 7: windows key followed by a left arrow followed by the enter key. Successfully completed shutdown process
Windows 8: involves jumping through numerous hidden menus, and I don't think can be completed using just the keyboard short of launching cmd and entering in shutdown /s
Windows 8 does countless things like this: makes it take longer and involve a convoluted process to do simple tasks all in the name of "user friendliness". There's absolutely no reason launching any arbitrary application should involve first going through a paradigm shift in the user interface.
To clarify: On an ARM tablet, where all you have is the Metro interface, I think Windows 8 will be decent. It's mixing of the interfaces on x86 that causes all the problems. To say nothing of http://www.wired.com/gadgetlab/2010/10/gorilla-arm-multitouch/ when using a desktop or laptop with touch display. Apple, which, for all the flaws I see in that company, realizes how horrible it is from an ergonomic standpoint to use touch devices on vertical screens for prolonged periods. Microsoft is the only company stupid enough to consider it.