Justas Ingelevičius wrote in about an Autodesk international user group poll about non-Windows ports. Specifically, users want Autodesk Revit (engineering design software) to run on Mac OS X and GNU/Linux. As Justas writes:

We have to handle projects sometimes ~1GB of size (whole districts with 20 levels buildings completely 3D) in Autodesk Revit Architecture and let edit that project for many users on network. Work speed depends on effective management of computer and network resources. It definitely will run better on Linux, then on Vista or Xp. We invest much in good hardware and high speed LAN and it’s ridiculous, that we have to run windows…

In other words, the interesting question is not “Would you pay for proprietary software?” or “Can proprietary software exist with free operating systems?” but “Your software is the only thing keeping us on Windows; can you sell us what we really want to buy?” It’s easy to predict that this conversation will happen more frequently and with greater volume. (I imagine something similar happened when Windows NT was worth using and much, much cheaper than high-end UNIX workstations.)