This software is only really useful to me, if its units can be defined as centimetres or metres. It's my main complaint about many of these 3D modellers, like for eg, the otherwise excellent Cheetah3D, units come in one package only- completely useless for architecture or engineering purposes.
A far better bargain in my honest opinion, would be ViaCAD 2D/3D, because units can be easily defined as standard units of measurement (VC also uses ACIS, the same 3D kernel as AutoCAD). Fortunately, SketchUp allows for this standard setup of units too.