Personally I've found that a lot of Win8 bashing comes from old-timers and people who, for some reason, expected to be able to master it in 5 minutes. Also, ignore the misinformation until you try it. It does not take "opening 4 windows" to turn off the computer, it's two clicks, just like before. If you have to google that for hours...ahem.
I installed it and never looked back. As mentioned, it's lightning-fast on startup. Bringing back the start bar takes five minutes. I find the OS to be overall noticeably quicker, just in navigation and launching of tasks. Also, I hope people have at least tried the "metro" apps; some of them are really nice. I can have an app running (for instance) live TV, and snap it to the left side of the screen, making it totally outside the frame of the rest of the windows so its never hidden. The NYTimes app is awesome, the default weather app is nice, I'm sure there are tons of useful ones I haven't used yet.
I happen to like the new "flat" look to the interface, it's much cleaner than having a bunch of pointless bevels and "glossy" effects everywhere. It actually makes OSX start to look downright ancient.