The Blender Foundation has just released the first ‘beta’ version on the 2.5 tree, version 2.53 beta, representing the culmination of several years of work by the development community. They say it’s feature complete for the most part, and the only reason it’s still Beta is due to some issues with the Python API.  The new version has a completely new GUI, redesigned to be clearer and easier to navigate, as well as support for Python-based addons and user-definable keyboard shortcuts.

blender.org – Blender 2.53 beta.