Update: The author of the device detection code has been identified! Max Horváth dropped me a note letting me know that this lovely little bit of code was written by him. He's got a great blog that often covers iPhone SDK material also.Somebody asked me over Twitter for how to detect what device the code was running on. Since a tree fell in my backyard the other day, right on the telephone lines and taking out my internet service in the process, I was working on an iPhone, and trying to answer a question quickly.
In short, I gave a wrong answer. My apologies to anybody who relied on it.
Here's some code, written by Max Horváth, that detects the device model correctly.