I'm typing this on my windows 8 laptop right now. I will say that metro occasionally does something pretty but is largely useless. I usually get into it by accident and not by choice. I consider it kind of like the media center interface for windows 7. Something you might engage by accident and marvel at for a moment, then try your best to turn off (at least if you're using XBMC or some other media center replacement).
Reasons for using it: It really is faster than windows 7 at several tasks. Booting for one. My laptop has an EFI bios and I installed a solid state drive. It boots in 2 seconds. It also updates far less frequently than win7 and has to reboot less, but that may be just because they haven't found all the bugs yet.
Way to use it: Get classic shell and configure it to skip metro
Things I hate about it: The windows 7 search functionality is broken from the start button. I think this is a classic shell limitation. I believe if you actually use metro and type a search it will be like win7. Basically it doesn't properly search for programs and other things so if you're used to hitting windows key and begin typing name until completion happens, that doesn't work right.