Adjacent comment. I've found working in a true posix environment is drastically better than the oddities I dealt with Win32. One annoyance is Microsoft has never been able to implement fork().
Though i never messed with x11 as I was never motivated to see what it was like under the figurative hood.
From my experience, the number one culprit of legacy code breaking is someone asking if anyone knows how it works. Second most common culprit is someone making a "quick patch" to legacy code.