I've never tried Sketchup, but from watching the Silhouettes video, the approach of generating a 3D object from 2D vector profiles seems very intuitive.
Don't know how it would work for more complex objects, such as a screw with threads.
Back in the early to mid '90s I cut my 3D teeth on Ray Dream Designer's Freeform modeler. It's nearly identical to this modeler. In Ray Dream you had a three-sided box. You'd draw shapes on the two walls and floor and the program would create the 3D shape. It was pretty powerful for being such an inexpensive app.
Ray Dream went on to become Carrara, and I think it still uses the same type of modeler.
Hi Steve...
I have Ray dream Studio.. It was a pretty cool modeler.. Your refering to the "spline modeler".. It would create objects by sweeping cross sections along a path with spline guides from a top and side projection.... Although, MoI is far more powerful in it's modeling toolset.. The other thing is MoI is a NURBS modeler and RayDream was poly's...