I have used Autocad for PC on a Mac using VMware and windows.  It runs really well. In fact when I am ready to upgrade Autocad next if some of the features aren't brought into the Mac version I will run it on a virtual machine.  The only tricky thing about doing it that way is making sure you can plot print to pdf properly.  I am out of the loop on that issue, i used Cutepdf for PC back then. There are plenty of resources and experts here to help guide you.

In fact when I ran AC 4 PC on my mac. it ran better than on my PC with similar specs.