Not sure if this is still active but here is my perspective. Sketchup is more of a modeler program, not a program to generate precise construction drawings. It's also mostly about rectangles. It's also clumsy compared to a good CAD program. By that I mean you are working in blocks rather than with lines. And the lines in SUp often don't connect with each other in export files so you can't get good CNC file output.
I think of drawing programs in 3 levels:
- Modeling for ideas, concepts, renderings
(SUp, Illustrator, Rhino, Cinema 4D etc.)
- Designing a Single Product for Mfg.
(Vellum, Inventor, Solidworks, etc.)
- Designing for Full Integrated Mfg. with a database
(CATIA, Solid Works, Autodesk, etc.)
It's important for newbies to not start down the wrong path with the wrong software.
I use Ashlar Vellum Graphite (2d) and Cobalt (3d) on a Mac. These programs are often used to do initial design work before taking the output into a database driven program like Autocad or Solid Works. This is primarily because the Vellum user interface is very intuitive and user-friendly, has powerful tools to work with non-linear edges/faces and has accurate output via a wide range of file formats. It's also easy to learn and you don't have to be a CAD jockey 8 hours a day to master it. Autocad is a great program for architects but it's a beast to learn. Vellum programs are great for part time CAD work.
If you read the critical user comments about SUp you see problems that are not general to a quality CAD system, like limits on internal resolution. SUp's main advantage is being free. However, this is like buying an inexpensive table saw with a 1.0 HP motor and a throw away fence and then complaining about the quality of your cuts.
My main point is to think about your CAD program as a long term investment like the rest of your shop equipment. If it's cheap, then it is missing something important that more expensive programs spent a lot of time developing. The other thing a cheap program will do is frustrate you as your skills grow and the inadequate program starts to sag.