I don't have a problem with Windows Explorer in Windows 8, in itself, except for the way it is so jarringly different than Metro. IMO, it is recreating the X11 problem of too many UI tool kits.
Personally, I think Microsoft should consider creating a Metro based file management system.
Metro is content- and context- oriented. It will present a file browser when you need one, containing the kind of content you care about. For example, add a picture to a tweet in your Twitter app and get an image gallery. The idea is for you not to have to care where files are located.
Personally, I think Microsoft should consider creating a Metro based file management system.