They start you off with the very basics, and within a couple of hours you can be designing moderately complex things. I don't know if my earlier experience with AutoDesk was a help or a hindrance. On one hand, I understood the basics of 3d modeling, on the other, I expected there to be tools for what I considered basic functions like countersinks, chamfers, and threads.
The printing time for the base component shown above is 5:25. The bulk of the design time was figuring out how the actual size of the printed holes vs. the theoretical hole size in the SketchUp model. Another challenge was the countersink of the the holes. A theoretical 1/4-20 screw fits into a theoretical 1/4 inch hole quite nicely. But when you actually print it, they don't work so well. Tolerances and clearances have to be built into the design.