As someone who has been an admin (both with and without that job title), I'll say that I was slow to change, and often still am. Why? Because every change is an opportunity for something to go wrong, and in my experience, something goes mildly wrong about half the time, and catastrophically wrong way more often than it should. This is after doing all the testing that can usually be done. Either there's no testing server for this client, or you can't replicate the exact conditions of the change because you don't have another Windows 2003 SBS handy to test interaction with, or you run into lots of issues in the test and can't easily roll back to make sure that you can do it flawlessly this time...

Unless you've got an employer or client that can afford you for an additional 20 hours for each major change, everyone involved just crosses their fingers and holds their breath. I've never been an admin in an environment where there was adequate funding, though, so maybe it's just me.

Anyway, I typically put off upgrades and new installs that affected old servers (new apache modules or whatever) as long as possible.

Edit: this is why I just code, now. It's easier to write stuff that works than to find the magic this-THEN-that incantation to make someone else's stuff work. ;)