I haven't yet used it, but I have heard great things about it and seen some really impressive models. It is a NURBS modeler, which I think is far more conducive to architectural modeling than polygonal. I just saw on the MaxwellRender forums that Rhino is coming out on OSX.
If you go to this site:
You can sign up to get a free Beta version.
beta tester since yesterday and it looks quite promising!
it sort of sketchup mixed with acad command. very precise.
i will try to import plan from my HD later...
by the way did you get my pm?
and if you wanted to check the Novus contest result (which i draw plan and detail with HD) there's a url : http://www.creativitemontreal.com/article.aspx?id=22903