GW doesn't update their FAQ/Errata that frequently though. If they made a 'sticker-product' (sold for the BRB, and each individual army-book) in an ultra-thin transparent adhesive material, that would become almost 'seamless' on the margins of the relevant pages - then I would definately concider using that depending on what the price would be.
Of course, this all falls together when concidering that it's actually the IoB-rulebook that is kept on hand at the gaming table - but would still be nice to have to in the Big one.
Everyone and their mother has a tablet, phone, or computer nearby, and it's easy to print out the sections of Errata that you need - it's just sometimes things are so minute it's kinda hard to remember 'to look' for the Errata-amendment. This would be allieviated a bit with stickers I suppose.
Not sure if it would be of enough use to be a worthwhile investment though.. Probably not.