They finally released the first alpha version! You can grab the official binary from the official website or compile it by yourself (here's a nice video tutorial: Building Blender 2.5 with SCons and MSVC on Windows 7 from Nathan Letwory).
Here's a more decent overview about the new hotkeys: http://www.blenderguru.com/whered-that-button-go/ written by Andrew Price from BlenderGuru.
Note that you can also download updated builds for both Windows and Linux from http://www.graphicall.org/.
Basic hotkeys
