MS are not forcing the Metro UI on anything but tablets with Win8. All signs indicate the traditional desktop is going absolutely nowhere and will be available on Win8 on the x86, it's just the ARM (WoA) Win8 that will be touch/Metro only. There was an 8,000 word blog post from MS just a week or two ago stating this. This has been stated over and over, but people keep ringing the doomsday bell for the desktop OS, and are blatantly wrong. Unless MS change something last minute, you will have the option to use Win8 in the similar and familiar way you've used every Win release in the past, in a mouse and keyboard, point and click, icons and desktop format. The RTM/consumer preview release comes out at the end of the month, so we'll see then, and I'm confident the Metro UI will be entirely optional on the x86 desktop. Your Start Menu is being tweaked, but other than that I don't see much difference than W7 than W8 for desktop users, at least until ReFS hits the consumer level MS os's, if it does.
Anything else would be financial suicide for a company with such high profits in enterprise. Enterprise sales is what made MS rich - consumer OS sales are nickel and dime compared to enterprise for them. Even the nicest to use (iOS, IMHO) touch/tablet interfaces simply are not an effective substitute for the desktop for productivity, and that doesn't even factor in dinky screen sizes, lack of processing grunt, and lack of storage and traditional connectivity found in a desktop.
I'm no apologist for Apple or any other tablet maker, but they are quite usable appliances, stuff like the iPad. Note the "appliance" denotation - you are not going to replace a traditional computer with a tablet anytime soon, which they can both do a lot of shared tasks, there's some things that tablets simply are not productive with, like heavy data entry, content creation, etc. A tablet is a computer, but in a lot of ways it simply isn't - it's a consumption device first and foremost.
Many people slamming tablets and touch devices are viewing said machines as desktop competitors, and in my books they simply can't be compared. Most guys derping and whining about touch keyboards and tablets in general being entirely unusable in any capacity have never even tried them, and are likely still the types to own 7 year old feature phones
They aren't for everyone, but even the naysayers would find them quite usable even after using them for an hour or two or they simply wouldn't have taken off like they have. For emails, quick docs and such, tablets and their onscreen keyboards are more than usable, and I dare say pleasant to use if you understand what they can and cannot do.