User experience,interface as well as compatibility (Mac, Windows and Linux) is key, the rest will come later (unless you heavily fail on it)
As written before, I don't have the time and hardware to bother with Mac os.
To be honest though, that’s a dumb decision — a good app that runs on the #1, #2, and #3 desktop OSes is a lot more valuable than one that runs on #1 and #3. Even more so as the Mac platform has continued to gain ground outside of its classic stronghold of media production. (Almost 10 years ago, I worked at a software company that made a Windows program for research and academia, and we got daily inquiries into a Mac version. For many customers, especially large ones seeking site licenses, the lack of a Mac version removed our product from consideration entirely, as all our major competitors supported both. Linux inquiries were but a tiny fraction as many as Mac.)