I've never used AutoCAD products, but I found Sketchup to be miserable and very limited. Solidworks is pretty similar to most of the other powerful solid modeling software out there: CATIA, Unigraphics, ProE, etc. One you learn one of them, you can pick up the rest pretty quickly. Give it some time and you'll see why industry uses these applications and not something like Sketchup (again, I can't comment on AutoCAD).