This is great both because it is free and also since it works with Mac. IES have been going for a while in the UK and they have a
sketchup plugin which is also free, but PC only ... and now looking around have a
link to archicad via gbXML as well.
Re your original post, the funny thing is that sketchup led me directly to archicad. Having been (effectively) a flat-cad vectorworks user for 14 years I really got into 3D possibilities with sketchup earlier this year and quickly realised that I needed something more robust to take me to the next step - hence archicad. With multi-million jobs on the line sketchup would have a very long way to go in the BIM space. Considering the non-BIM but BIM-marketed vectorworks I do not think you can change the nature of the beast. Sketchup is very good at what it is but I'm guessing that customers will pitch them against the likes of bonzai rather than the more comprehensive BIM packages.