Yes, you shouldn't do Ruby development on Windows if at all possible. But is there any reason why OS X is not mentioned in the Linux section? It is after all what many Ruby developers use.
Poor phrasing on my part. What I meant is to have an OS section and then discuss Linux and OS X as the two main options or mention OS X as an alternative, if Linux is the OS he intends to promote in the section. He could also mention non-Darwin BSD.
Linux is mentioned because it is a common server OS and Linux knowledge is the most helpful for web dev. OSX do not add any extra value to this aspect of knowledge (despite I do use OSX as desktop OS).
