I cannot tell you how happy it makes me to open a terminal window on OSX and type "ls" instead of "dir". If I never see another DOS .BAT file again it will be too soon.
Yup OSX is Unix, but like all other flavors it's got unique quirks. If you want to play with the various distros, I'd suggest
Parallels or
VMWare so that you can install (and run!) multiple OS'es at the same time without rebooting nor installing from scratch.
Good luck with your programming. If you're taking suggestions, I could really use an aim-bot for
Nexuiz.