There's a lot more to Windows 8 than its user interface. In a normal Windows release, these other aspects—a new storage subsystem that lets you join multiple disks together, a new backup system, reduced memory usage, greater protection against security exploits, portable installations on USB memory sticks and more—would be prime considerations when assessing the operating system.
In the coming days, we're going to take a closer look at some of these features, but the user interface changes in Windows 8 threaten to overshadow them all. Some people have had visceral, negative reactions to the new user interface, and they're more than willing to forego these other improvements so that they can stick with Windows 7's much more familiar face.
If you're a desktop user, then yes: the new interface is not perfect. Despite what Microsoft says, the new interface is a compromise. The new interface makes some things worse. It also makes some things better. If you're a multimonitor user, I would think long and hard before upgrading; as welcome as the new taskbar is, the ease of use of the new interface is a severe problem with multiple monitors.
With a single screen, however, just treat the Start screen as little more than app launcher and be selective about your use of Metro, and it turns into something that actually works pretty well. Maybe even something better than Windows 7.
That may not be enough for everyone, particularly in corporate environments scared of retraining costs, but Windows 8 shouldn't be dismissed out of hand. Should you go for the new operating system, you won't lose any performance, and you can even get away with an in-place upgrade.
If you're willing to look beyond the desktop, Windows 8 offers something altogether more exciting. There have been hybrid and convertible laptops in the past; machines that can switch between being what is essentially a laptop and what is essentially a slate/tablet, typically through some form of docking keyboard or exotic hinge mechanism. These machines have always been better laptops than they were tablets due to the weaknesses of Windows interfaces of old.
Windows 8 lets these machines become truly useful. In their tablet guise, they have Metro apps (though these are currently a little thin on the ground). In their laptop guise they have full-strength desktop software. There are still rough edges. The integration of the two interfaces needs to be better. But Windows 8 works. It's one operating system that can support tablet and desktop apps side-by-side. And that might just be worth a little compromise.