I installed Win8 back in November when it first came out because I needed a new copy of Windows and it didn't seem to make sense to buy a brand new copy of 7. I gave Metro an honest try until January, when I broke down and installed Classic Shell, a program that brings back the standard start menu and lets you turn off a number of the Metro-isms.
Unfortunately, Metro sucks on anything that isn't a touch screen. It adds unnecessary movements, clicks, and searches to find things are easily accessible in earlier versions of Windows. It's awful in terms of organization, and it's jarring to move back and forth between anything that runs on the old desktop and Metro apps. The fact that it's non-intuitive to people have used older Windows is a forgivable fault (like the ribbon interface on Office); the real problem is that once you find everything again, it's still less efficient (for desktops and laptops). I also find it highly aesthetically unappealing, and feel a general repulsion to the "app store" they are pushing.
But now that I've gotten rid of Metro, and started customizing things, I can honestly say I like Win8 a lot. It's quick to boot, stable, and efficient with resources. It has a lot of nice new built in features, like the upgraded Power Shell. So far, the built in security have been useful but reasonably unintrusive. It's also compatible with almost all Win7 drivers and older software, so the upgrade has been pretty seamless.
The bottom line is that Windows 8 is really nice under the hood, it just has a really ugly hood. It's a Lexus trapped in the body of an Edsel. Overall, I would say it's not really good enough to upgrade if you're already on Win7, but I also wouldn't buy a new computer without Win8. If you're willing to put enough time into customizing the interface, it may even be your favorite Windows yet.