One thing I find fascinating about the aD documentation is that it is easy to learn and emulate, so that systems developed on top of the aD infrastructure can easily have some documentation. So, the initial documentation may not be as nice & useful as the books you can read about other systems, but I think the documentation of the actual product you end up building is far better than a product developed with another system where no documentation is done on the customizations/extensions/new modules. I hope that if overall documentation is improved, this ease of emulation won't be lost (i.e. improvements would be via better ad_proc comments or some other easily emulated & maintained system instead of glossy books)
