Specifications can be found in the GL registry: http://www.opengl.org/registry/
NVIDIA drivers already supporting it as well as new ARB extensions can be found there: http://developer.nvidia.com/opengl-driver

A full and very good review can be found on G-Truc Creation: http://www.g-truc.net/post-0414.html
Among interesting things, the shader_atomic_counters, conservative depth, instanced transformed feedback, the integration of shader_image_load_store and more !

And congrats to Christophe for his first credit in the spec :-D