gentoo linux is my favorite because you build everything from source and it so soild reliable and secure (well if you make it that way since you do everything yourself durring the install) but due to time constraints I've been using Debian and Ubuntu linux because they work relativlely well and are fast to install
Mac OS X It has all the power and flexibility of Unix, impeccable hardware suport nad it runs all of my design programs. While having FAR less overhead than Vista.