yes, I use the pro version. Theres some cool differences, though I don't know them all off hand since I don't use the free version. Pro has a terrain feature that allows you to sculpt mesh into a terrain. I think most of the other differences are in export functions. Theres a tool with pro 6 called "layout" which allows you to create presentation pages from your models.
Honestly, unless you're going to make money off the work you do in sketchup, the free version is just fine.
Here's a finished model I just did that was created in sketchup, ported to viz, then rendered in vray.