Here is what I think of it after trying the developer preview and the release canidate
Pros: Start up time is faster, new login methods, simpler areo effect, Ribbon interface on windows explorer(love this), updated task manager,...
Cons:Metro is ugly and bulky to use with the mouse, have to scroll sideways instead of up and down, ability to have advertisements on metro, can become really messy once you start installing a lot of programs, no windows 7 start menu, settings and stuff have been moved around, no option to disable metro.
Final thoughts: With all of the tablet craze, Microsoft seems to be pushing for tablet based OSes on both tablets and desktops. Their mistake is not letting people disable certain features. I love the new windows explorer additions and similar stuff, but metro is just awkward and annoying for me. I would say that windows 7 is the better OS, and you should wait until Microsoft comes out with their next OS, and skip Windows 8.