A few days ago McNeel has released a new version of the Rhino 5 beta (although I’m not sure how much longer they can call it a beta when they state that it is now MORE stable than Rhino 4). The new version includes some great new features involving the implementation of python as a new scripting language for Rhino. Check out the new python scripting subdomain on Rhino’s site..
In addition, today David Rutten released a new version of Grasshopper (either called 0.7 or 1.0 WIP). This is a major release for grasshopper so many things have changed. Specifically, custom scripts will probably have to be reworked as the underlying connection to RhinoCommon commands has changed.