Vali Architects puts out some fantastic scripts for use in Sketchup. I have the Instant Roof script and it works really well for creating roofs in Sketchup. Of course after a roof is created in Sketchup you can't easily modify it like you can roofs in SoftPlan but it is easy enough to erase the roof and recreate it. This could also be used to easily create exposed rafters for use in Sketchup or SoftPlan.
They recently came out with a new script called Instant Wall. I watched the demonstration video and was very impressed. I can see where this could be used for a large number of instances to create components to be used in your Sketchup or SoftPlan projects.
Check out all their scripts at http://www.valiarchitects.com/sketchup_scrips
Bill is the owner and maintainer of SoftPlanTuts.com