I don't pretend to be on top of all the work done in the Mono world, but this strikes me as being the first comercial application that:
1. is advertising that it supports running on Mono
2. has gone through the work to test on Mono,
and I suspect,
3. has probably worked w/ getting fixes in Mono in order to allow it to run properly.
I think this is a cool milestone for the whole Mono effort.