I suppose I can agree with that, but as you said that has nothing to do with the companies themselves, and more to do with third party communities working towards intercompatibility. I wouldn’t really count that as a point against Apple, nor a point for any of the other OSs.

I will, however, admit that Linux distros tend to be cross compatible, but that’s more because they haven’t diverged “enough” from core Linux.

Though what I really meant by that, was that you can’t take a compiled executable from one OS and move it onto another, and have it work without some sort of compatibility layer.