Actually, to cover everything the various flavors of IOS does, you would
probably need different nutshell books targeted at different audiences,
perhaps one for each flavor of IOS. (Enterprise, IBM, Desktop, ISP...) I
don't think too many people on this list would care about the SNA $%#^ that
Cisco-Blue does.
Its easy enough to put a note at the beginning of each section or
perhaps some kind of icon that refferences which release a given
feature is in.