I've used so many operating systems, it's a joke. Here's a non-exhaustive list of OS's I've had moderate to extensive experience with:

MacOS X/Classic, Windows (all), OS/2, BeOS, Most major linux distro's including a custom kernel roll, Free/Net/OpenBSD (my primary OS before I got a mac), Amiga and Sun Solaris.

MacOS X is the clearly superior one.