To download the evaluation version:
"This fully functional version is the same as the commercial version except that it only saves 25 times. After that it is still fully functional except it will not save. It will still work great to learn Rhino and as a viewer for Rhino and many other file formats."
http://download.rhino3d.com/rhino/5.0/evaluation/download/
To order your copy follow the instructions here:
http://www.rhino3d.com/sales.htm
As we have been testing the beta releases for a long time, hopefully a service release will be released in a few months as v5 still has many features to be fixed to work better.
