The work under the hood focussed on cleaning up the Xfce codebase, and removing old and deprecated parts. "Xfce 4.8 is our attempt to update the Xfce code base to all the new desktop frameworks that were introduced in the past few years," the Xfce development team writes, "We hope that our efforts to drop pieces like ThunarVFS and HAL with GIO, udev, ConsoleKit and PolicyKit will help bringing the Xfce desktop to modern distributions."
A major new feature is the ability to easily browse remote network shares using a whole variety of protocols, such as SFTP, SMB, FTP, and so on. If you are performing several file manipulation operations at the same time, their progress dialogs will be merged into one.
The Xfce panel has been completely re-written, with better positioning, transparency, and item and launcher management, without sacrificing compatibility with the Xfce 4.6 panel. New is a plugin which allows you to browse directories (in what I would call BeOS-style). The settings panel has also been overhauled.
"The display configuration dialog now supports RandR 1.2, detects screens automatically and allows our users to pick their favorite resolution, refresh rate, rotation," the team writes, "Screens can be configured to either work in clone mode or be placed next to each other. Keyboard selection has become easier and more user-friendly. Also, the manual settings editor has been updated be more functional."
Xfce 4.8 will make its way to your distribution of choice, but of course, you can always just go and build it yourself.