I love Rhino as a concept sketching tool. All drafting programs that I tried started from an esoteric point of view...had to learn their specific way of getting things done within the program before you could actually do something. Not so with Rhino. Rhino begins with a basic knowledge of drafting. If you know how to draft, you can be productive with Rhino instantly...for the most part, the steep part of the learning curve has already been tackled. Rhino is essentially an electronic 3-D drafting program. Moreover, the program is fun to use and nigh impervious to breaking (as opposed to Autodesk's Inventor, which in my hands was always on the rocks). I recommend it highly.