The NY Times uses both "on Mac OS X" and "in Mac OS X". Can someone explain which one seems more appropriate if there is no difference?
To me, at least, "on Mac OS X" refers to things that run on top of Mac OS X, while "in Mac OSX" refers to things that are part of Mac OS X.
In computer terminology, "on" typically refers to things that involve a "platform":
"In" will refer to specific programs, stores or components:
The confusion around Mac OS X is that it qualifies as both a platform and a specific piece of software depending on context:
So the correct answer is that it depends on the specific usage. David Schwartz's answer provides a good rule of thumb for determining which usage is correct in a given scenario.