Mac OS X is the best operating system on the market today by offering more features than Microsoft’s future Windows Vista already at its 10.4 Tiger version. 10.5 Leopard version is scheduled to ship next Spring and will offer tons of new features like Safari’s integration with Dashboard, Spaces, Time Machine, a new version of iChat and Boot Camp.

I use and Debian only, as a matter of fact i use debian testing in my testing server enviroment, Debian current stable for my live server, and debian unstable for one of my desktops.

I have never had a security issue with Debian and i have been on it for 5 years. I have tried others Cent, Slax, RedHat, SuSe, Mandrake > Mandrivia, i did not like any of the others (Obvious) and stuck with Debian.

I even use Debian as a dataserver for several people using MS Access to use the database, NFS Here where i am at and at several locations. I have even put a Doctor on a linux enviroment with some medical software solutions. All of this stuff is protected by Vyatta Router software on a old P4 computer.

Well, my friend who is working as Technical support, and also have his own webhosting, uses Suse Enterprise as operating system.

RedHat Linux is the best.
 

RedHat Linux is the best. Although I have never tried CentOS but I don’t feel the need of changing to any other OS since I find RedHat to be very user friendly, fast and reliable. SO far no critical problems so no need to change OS.

It all depends on the things you are planning to do with the computer imo.
If you are someone who wants to get anything to work without doing much/anything you should choose Windows, as most applications are (only) compatible with Windows-systems.

If you are someone who loves to experience you should choose Linux, it's fully/almost completely editable as it is open-source. And it is very fast, even if you haven't got the biggest RAM memory.

And last but not least, if you are a creative person, you should choose Macintosh as it supports many creative applications and provides the best support for such apps.

Re:
 

You should also look into your budget if your budget is enough then you can get window otherwise linux hosting best option.

Ubuntu ftw.. but i currently use linux mint 12 (lisa). Yet there's new from fedora and ubuntu its called Fuduntu but I have never tried it xD