Searching by metadata or even full content (for some formats such as plain text, Word, Excel) was already present in earlier versions, even XP I think.
Spectre's right about power features. But actually for that kind of thing there's PowerShell (which is an optional Windows update):
http://www.microsoft.com/powershell
And as long as they continue providing good support for 3rd party developers... That's been the key to Windows' success since version 1.0. Of course other OSes have to come with more utilities built-in, and yet you can't find as many as for Windows.
Windows 8 for PC is different from the mobile version--actually it includes that (apps and tile start menu) on top of a normal 6.x Windows. The only difference is the tile start menu, which IMO is a big usability improvement over the traditional cascade one (and that you can run "Win RT" apps, as well as normal Windows desktop programs).
The tiles are just shortcuts located in the same exact paths as the start menu shortcuts in previous Windows versions. Both apps and desktop programs create tiles, the latter when they would create start menu shortcuts in previous versions. Of course in mobile Win8 it's different, but so's in Android or iOS.