Have you actually tried it? LOL!
I recommend you do, it's free you know. Most people seem to bash Win8 because it's a cool thing to do now. 
Most people bash Windows 8, including virtually every game developer on the planet, because of the OS itself. It has nothing to do with being cool. It has everything to do with how bad the OS is. It represents a giant leap forward in Microsoft leveraging more control over your computer.
The team developing Windows 8 is the same team that did Windows Vista. The team that developed Windows 7 is working on what comes after Windows 8. My bet is on that OS.
However, to shore up any risks, it is best to go ahead and invest in Windows 7 now (while you can still get it), and let Windows 8 die on the vine and see what comes after that.
People who claim people are bashing Windows 8 to be cool offer nothing more substantial than those who mindlessly rant about it. I take either with a grain of salt.
If you like to play games, you might pay attention to what every game dev has to say about Windows 8. None of them like it and for many good reasons.