i run mostly 8gb cards too, a few 4s here and there for festivals and such
what does the update do? allow the 671 to accurately say how much time is left on a card bigger than 4gb is all i can think it would be. not really an issue for me, but i could see that being really handy for you doing extensive recording times. ive only had one occasion where the show ran constant for longer than that, and i had borrowed an R44 so i wasnt running the 671
im almost thinking of ditching mine. i love the sound of the acm mod, but i really dislike the indiviual gain adjustment hassle in the dark at a rough show sometimes. ive got the itch for 4ch too, so its time to move on fairly soon i think