Great post OP. Another thing to do is make sure that the Datum in your GPS is the same Datum as the map you are using. If you dont do this, your GPS is worthless.
I agree that it is a good idea to be aware of the datums being used. However, for practical purposes in simple/typical land navigation, the common datums used in more recent times: NAD 1927, NAD 1972, and WGS 1984 are all going to get you very close - at least not lost. Of course, if what you are seeking is an old obscure trail - which is actually accurately marked on a detailed map- then the correct datum may make a difference.
