I've never heard of a college course on business that helped anyone in a startup. On the other hand, if there were one, it would probably be at Stanford.
From personal experience, I can say that a genuine course in marketing (not a 'how to write ad copy' intro to advertising) is absolute gold. Bare-minimum: Look for "M.A.S.H. Analysis" in the course outline.
To answer the poster's question: I'd say go for it. Worst-case, you're surrounding yourself with like-minded students.
My co-founder and I took a seminar on entrepreneurship offered jointly between the engineering and business schools at USC. It was actually pretty similar to YCombinator dinners -- every week someone (occasionally multiple people) came in to talk about their own experiences as an entrepreneur, answer questions. etc. Unfortunately, unlike YC, it was at 7:30 in the morning, which was tough.
It wasn't focused on software, or any one field at all actually, so there was a really wide range of speakers. I have a hard time remembering many of the individuals, but a lot of the overall lessons have stuck with me I think. I have a long set of notes I should really look over, I'm sure their are things that would come in handy right now.
Don't you have friends in your program to consult for advice? Assuming you're not in that program, isn't there any kind of forum for Stanford students to discuss classes? It seems like YC is unlikely to give you the feedback you are looking for in regards to such a specific question.
It probably depends on the professor: is this Gibbon guy a good teacher? Try to find out if he's taught the course before and how it went.
It's the difference between just learning cute terminology (bad professor) and initiating a real interest/solving hard problems in the subject (good professor).
To answer rms, I'm a stanford alum. I think the course is interesting enough to give it a shot - thanks for the advice. I'll be sure to summarize anything interesting I find.