It's not a failure. It's a change. I've worked as a tech for the past 10 years, and when you're dealing with people who don't know what a "restart" is, you're asking for trouble. I've worked with every type of person out there (the doctors, secretaries, bankers who type yahoo.com into the address bar, then in the search bar type in google, and once in google, they search for CNN... seriously), my conclusion after all this experience is that most people are technologically deficient. I've gone into an office for a printer installation just to find a Macbook Pro that hasn't seen a restart in 6 months, and the client is cursing his macbook for being so slow and always hanging.
Having said that, for the technologically inefficient, windows 8 is a failure. A huge failure. But for the technologically aware, windows 8 is simply a change. If you have a touchscreen and become proficient at using it, the system is fantastic.
I wouldn't go as far as comparing it to vista. Vista was buggy, laggy, inefficient. Windows 8 is different. It's not even close to how bad vista was and is.