As someone who works regularly with users for computer support, Windows 8 has been a nightmare for me.
The first problem was that all the changes were like having to re-learn how to walk. I couldn't do anything efficiently until I spent hours "updating my software" just to get my head wrapped around the changes.
That hasn't happened to me ever since my initial days working with Win 3.x.
The start menu was an addition that efficiently and cleanly organized a lot of options into a small area. The loss of open and closable groups on the desktop (of remembered custom sizes) was slightly annoying, but that was it.
Since Win95, the only real changes have been shortcut keys (damn you shift from CtrlAltDel to CtrlShiftEsc), and background processes.
The biggest issues though are how consumers understand their computers. One of the tricks I would show users previously was how to move all their "random junk" programs in the start menu into one folder, streamlining their Start experience and making it very quick and intuitive. As well as combining that with Desktop (and later, quick launch) links for the most used applications.
Now it feels like setting up anything where they have access to the tools they need requires pen and paper so they remember how to get to it all. No more "Start -> Programs -> Computer Trouble" to hide away all those programs, text files, etc, that they hopefully won't need (and don't want to stare at) for months.
Or when I ask them "how do you get to your control panel", after showing them, it usually involves them trying for 30+ seconds to get the side bar to pop up for them.
And as a dedicated user of multiple monitors, Windows 8 guaranteed that I'd never move past Windows 7. Win8 is a single-screen touch-enabled monstrosity that belongs in the handheld (tablet/phone) market only.
They promised us a "slimmed down" Windows that we would expand and customize to our needs. And yet most professionals I know involved in computer tech find themselves removing/limiting parts of Win8...
MS failed us with Windows 8. They're finally listening to what we have told them with our wallets, but I say "too little, too late". I'm happy with Windows 7. With the dropping prices of RAM, and increases in processing power from multi-core CPUs and 64 bit processing, the bloating still present in Windows 7 is entirely manageable at only minor cost. And that cost is far less than the drawbacks of "upgrading" to the next OS - especially when you consider the cost Microsoft charges for their OS software.