On Windows, plugging a device or peripheral into the computer could result in different types of actions, and sometimes, it was not clear how to get to the functionality a device provided. Devices that provided multiple functions, like a combined scanner/printer/fax, would show up as multiple different devices, making everything look a tad bit messy. Enter Device Stage.
Device Stage is a place where each device gets its own entry, and all its functionality can be accessed from one place. Manufacturers can brand their device's page. HP can, for instance, add a banner with a photo of the printer, and add links to cartridge suppliers. You can also edit what applications a device will use - you can set a Canon scanner to use the manufacturer's tool, or the built-in Windows tool. These customisations are stored in an XML file, so they should be easy to make. Microsoft is planning on offering a public repository filled with these XML definition files, so that they can be downloaded much like a driver is downloaded from Windows Update.
The new Libraries feature in Windows Explorer are similar to saved searches, with the difference being that you can write to them (you can specify the write location). A library is created by adding 'sources' to the library, after which you can sort in whatever way you want, very similar to early demonstrations of WinFS from 2003. Since I store all my media on a (shared across the network) external USB hard drive, this feature allows me to combine the content on my external hard drive with that on my normal, internal drive. In addition, when my laptops are also equipped with Windows 7, I can create libraries on them that span across the network.
Media Player and Media Center use the same libraries as the ones in Explorer, creating a more consistent experience. Ars does note a problem when it comes to Libraries in combination with email and contacts - while Vista Mail and Vista Contacts use individual files for emails and contacts, Live Mail uses a database, and doesn't work with Libraries.