I have submitted my first iPhone app and am now waiting for approval. My only fear is having it rejected because of some subtle nuance in the HIG, this is from googling around.
How does Apple treat the HIG, as guidelines or as gospel?
They are definitely guidelines, but if you don't have confidence or a good amount of experience with UX, you should treat them as gospel. When developing mobile apps, I kind of feel that providing a good UX should be the highest priority. A lot of developers are pretty bad at UIs, and the HIG provides a very good set of guidelines to follow, at least at the start. You should owe it to yourself to give a HIG a thorough read.