A little mediation about a few comments getting hot under the collar here...
PADI standards RE depth are aplied at the discression of the PADI dive center out side of courses. They make a pretty good guide line as they can help (or hinder) in a liability court case in the case of an accident.
Th state ment about only PADI AOW is incorrect, the GUE tech card wold almost certainly be equivalent or supercede a PADI AOW and as for the nitrox it generaly is taken up by advanced divers but an open water ticket with nitrox is actually still an open water ticket. Where I work ( as a PADI instructor) state law overrides PADI saying a diver must show a log book with 20 dives before doing a nitrox course, many have done their AOW by then or are considering it anyway.
More on that in a moment...
The guy who posted that PADI's depth limits are unclear wasn't paying attention in his OW class. Knowledge review for modual 5 spends half the questions explaining continuing education and depth limits. By this time in a course many classes are impatient with the "video, knowledge review, quiz" process (in this case exam) perhaps yours was rushed. Regardless of wether depth limits are enforced for certified Divers, the PADI standards on this matter are part of your evaluation, perhaps a refresher is in order.
Our Dive op dives a government controlled arificial reef, on this site it is LAW to stick to certain depths for certain experience levels, on our other sites...its a good idea to protect your liability insurance.
FINALLY, this thread is about presenting log books. Not demanded very often ( I wrote on a previous post about the declaration on the liabilty being a legal, signed document) but the NITROX laws in my state is an example of the fact that you might have to occassionaly.