Loyalty isn't usually something that should be associated with a corporation, but when it comes to preferred internet providers I've found it difficult to move away from my current one.
Right now, I'm with Internode. It's partly borne out of the fact that they were quick to host their own Steam servers and offer unmetered Xbox Live content, which five or six years ago was a pretty good selling point. They also used to host games.on.net, which I wrote for at the time, and that was a major factor for the loyalty.
With more and more ISPs behaving like utilities though, reducing the focus on customer service, loyalty seems a bit silly. And having just moved into a place that is due to get the NBN in (at best) six months to (probably) a year, it seems a good time to start shopping around.
What ISP do you have?