I played around with that last July. The most interesting feature is the subdivision smoothing that is integral to the product. I found it quite easy to model organic shapes, but not so easy to make some of the things I have done previously in SketchUp. That being said, I found it useful to create simple (or complex) organic shapes and then import them into SketchUp to work on them further.
The thing I miss most in SketchUp Free is the ability to run a simple script to pseudo-automate some sequence of operations.