sinc,
Just curious, have you looked at PowerCADD by Engineered Software? It's Mac only CAD program with a loyal following dating back to around 1988. It was called PowerDraw back then, when I used it.
No. But I've seen a few other CAD programs on the Mac, too, and there's at least a couple that have done 3D drawing (like what Autodesk added to Autocad 2007) for quite some years now. Easier to use than Autocad, too.
But I suppose I should've added that I need a Civil package. I'm using Civil-3D these days, so I would find it terribly difficult to use anything that is not model-based. I've actually been toying with the idea of creating one, a framework-based solution that is true multi-user for EVERYTHING, but it would be a large enough effort that I'd have to start a company in order to manage it. If Apple ever made their OS run on ANY machine that can run Windows, I'd feel a lot better about tackling the job, since practically the entire industry is using Windows machines, and no one would be very interested in switching to new software if it required trashing their PCs for Macs. But creating a multi-user CAD program would be quite difficult without being able to leverage EOF, and EOF only exists on Mac OSX these days. So the effort would be prohibitively difficult on Windows.