Well you are right about it?s hard to find a successful commercial software for Linux, simply because there are so many good free alterantives like OpenOffice, The Gimp, Firefox and so on.
However there is still no good cadprogram and that is also the only reason for me and some of my architect frinds to be held back to Windows. I cannot belive that we are the only one intrested in getting a good cadtool on Linux. A switch to Mac is not intresting me, what has changed if one do that? The OS, but not the freedom how to use that OS.
On the architectfirm with around 60 persons where I work, we consider the software beeing a costly part in our budget. Linux is a very intresting alterantive, it has all programs needed for our work except a good cadprogram.