I was a GM on Delloman's WoW server before it shut down.
After it shut down I created my own WoW server. My server was pretty damn good as far as functionality goes, I modded the shit out of it. But I just didn't have the bandwidth to handle many people. So I stopped doing that.
Shortly after I started playing on
http://wwwchaoticdesignz.net. Awesome ping, run on AMD64 with 4 gigs of ram. Very, very, nice server.
Within a few weeks of playing on chaoticdesignz and getting a Paladin up to level 83, they made me a GM on that server as well. I was a GM for a few weeks until some twerps started saying things about me using my GM char to give my other account items and stuff which simply wasn't true (I had all my items before I was even given a GM account). But chaoticdesignz is run by a bunch of 16 year olds who aren't the sharpest tool in the shed, so to speak. So they removed my GM status and I stopped playing there.
My conclusion is, don't bother with private servers, just fricken pay for WoW. You will enjoy it much more.
I'm never going to play on another private WoW server again unless I'm a GM, because being a GM was actually pretty fun. Hours of entertainment going around the map at 10x speed and changing NPCs to different models and making them bigger, etc.

Also fun coding in custom NPCs which do new things.
I was going to upgrade my computer system to AMD64, 4 gigs of ram, 100mbit line, and start my server back up, but Blizzard is really cracking down on private servers now and being in the USA, I don't want my ass sued.