although I never did go take the class (not yet anyway), check out
this thread...
hope that helps a little.
Like I stated in this thread, I think Nitrox is well worth the expense. Even if you don't want to go through the hassle and expense of owning your own tanks, you can rent nitrox tanks at most shops and charters for a few bucks more than air. I believe it's worth it when you consider the added cushion against a possible DCS hit and the extended bottom times allowed, especially on repetative dives, when compared to air. Also, the class helps improve your knowledge of dive physiology.