After using the PDC Windows 7 build 6801 for a few days now, one feature I have already grown to appreciate is Libraries. The Libraries provide a view of the filesystem that is tailored to specific content types. By default, Libraries are created for communications, contacts, documents, downloads, music, pictures, and video. Each Library presents its content in a style that's most appropriate; the downloads Library, for example, lists the URL that each downloaded files came from (or at least it will; currently the column doesn't get populated correctly), the contacts Library shows e-mail addresses and phone numbers, and so on.
These special folders (and their special views) will already be familiar to users of Vista. Where Libraries differ is that they're not individual folders. Rather, each Library is an aggregate of many different folders. By default, these will typically be each user's content-specific folder (Pictures, say) merged with the Public content folder that Vista introduced. You can add to these as you see fit; I'm going to add my media shares on my home fileserver, as well as my removable hard disk full of music.