How good is OS X as OS for a web hosting server? Please advice.

I recently installed a piece of software called MAMP... Mac Apache MySQL PHP. I use it for testing, developing, learning and it's great! I tried other tutorials to enable these 3 technologies on a Mac, but never had much success until MAMP.

http://www.mamp.info
Not com, org or net.

I don't know how it'd be as a public web serving environment.

An OSX server truly kicks butt! The server along with the OS supply all the necessary solution that you might need, but this is on a business level and can run into the tens of thousands of dollars.
I think you want to know if you can run small scale on your desktop. Most of what you need is already on your system and in most cases, anything you need can be found free with a bit of looking and implementing X11, which is provided on you install disk. Yes, it too will kick butt on a smaller scale too!