I love waiting like a month or two after it's released before upgrading. I got my 4S the same way. 4S was actually my first iPhone.
That way I can see everyone freak out, get their phone, and within a few days just go back to normal. I don't like being involved in the madness of iPhone release day. I still have my 4S and I still love it, so I'm not going to be rushing into line. I've been able to upgrade since mid August.
Also, because I'm crazy, I like reading posts that people make about things they like/hate about the newest iPhone, when its released and when they get it. Certain QC issues, thoughts about the phone, differences, pros/cons, etc. Then I like seeing the iPhone in person and looking for myself, then I purchase.
I can actually be a pretty impulsive buyer, but when it comes to my phone there is a process I go through. I can't blindly preorder an iPhone, even if I know what it looks like. I wait two years to upgrade so maybe that's why I'm more picky.