I think that a lot of people who love the Metro interface must have upgraded from XP to Windows 8, and so attribute improvements in previous versions of Windows to the Win8.
Power users should like metro better than the start menu. Once open, you just start typing and the app or file you intended to work with is ready to launch after about 3-4 letters typed. Its like a full screen graphical console.
That is not a Metro feature. It has been in all Windows since Vista (with the exception of the part where it takes up your entire screen). The difference was that Win8 split the results into files, apps and settings which then required more keystrokes (our mouse clicks) to get to the entry that you wanted. The 8.1 restored this functionality.
With metro the 5-6 applications that i use really frequently i can pin right in front of my face instead of digging through folders.
Whereas from Vista onwards, your 5-6 applications that you use frequently would be automatically shown on your start menu without having to pin them (although you do have that option too).
With 8.1 metro, my "start" area doesn't get bogged down with a bunch of bullshit just because I installed 1 new app - a BIG WIN in my book.
Once again, this is a Vista feature. Like Metro, you have to go into a different section to see the full start menu that we knew from the days of XP and earlier. But installing a new app will normally just add a single main icon to your start menu, and you click on "All Programs" to see the full group of icons. The difference with Windows 8 is that it is not obvious how to get to the full list of programs in Metro, although the 8.1 upgrade did give a small down arrow button to get to it.