You might be surprised, my first medical app on Qt was targeted to OS-X, for a whole year, but as Director of Software Development, I chose Qt to hedge my bets against the day that OS-X got thrown under the bus for "business reasons." And, yes, especially in 2006, the Qt App was still in Carbon, while Cocoa was what all the cool Objective C kids were doing that week - and our in-house OS-X champion threw a hissy fit about it. Nobody else cared - it was a good looking app, just not quite up to the minute with latest OS-X styles.
So, two things happened by mid-2007. One, Qt updated to use Cocoa, and 95% of the OS-X champion's complaints about the app were solved for us by the trolls - zero code changes required by us. Two, the suits decided that we were merging our design efforts with a larger project that was Windows based, so OS-X did get thrown under the bus, as predicted. It took about 8 man hours to convert our Qt App from one that was written on OS-X, exclusively for OS-X, never tested on anything but OS-X, to running identically on Windows - and 7 of those man hours were wrapped up in converting OpenGL code....
I'm in medical now, and the primary target is Linux - but lots of use cases call for operation under Windows too....