No better program
I have been using Rhino for a couple of years and I got to say that it is by far, the best modeler I have used. I have used SDRC, Pro/ENGINEER, and UGS, but Rhino actually listens to their customers and builds the program around them.
Rhino 4.0 has many new features and fixed a few old bugs. For the price, there is nothing else better out there.