I breath a sigh of relief every time someone combats the "use open source" with "blah blah blah, AutoCAD, blah blah blah". It's like you're reading my mind.
AutoCAD has barely acceptable performance when running on *great* hardware, let alone a virtualized instance or whatever concoction the avoid-windows-at-all-costs crowd would come up with. Not to say the grandparent-commenter falls into this category but very often people do.
When people step into my computer room they usually note the PC, macbook, G5 and solaris box and give me the 50 questions. My usual response is "AutoCAD, travel, Final Cut/Logic/everyday use & ZFS storage pool".