Mike
Have you ever tried Google Sketchup? You can do 2D and 3d renderings to scale with it. I started playing with it when we finally settled on a floorplan. It allowd me to fairly easilly model the house in 3d so we could virtually "walk-thru" the floorplan and better visualize what we were commiting to

I use an older version of autocad to do most of my design work, but found sketchup pretty easy to learn. Lots of Youtube tutorials to help get you started.
Commercial design? I would say most probably use Autocad...