Well, to be honest, for me the ideal day would probably be the last Friday in October (for them to arrive at GBAx, at least), since I don't have any lectures after 10am Fridays, so I'd almost certainly be able to pop down to the presumed party-thing.
I'd be happy to wait a little longer than that, though, if necessary... though the anticipation is getting more and more unbearable as time marches on!
In terms of updating firmwares and such, I'd personally be happy to do this as much as necessary, as long as the chance of bricking the unit is kept to a minimum - i.e., seeing as we now have 64Mb to play with, it'd seem to make sense to install firmware updates without wiping over the existing firmware, and have a built in module that triggers if there are more than one to select which to load. Then, once you've assured yourself of a successful flash, deleting the old firmware for space - or keeping it for comparisson.
Would also be useful, of course, for bypassing Linux completely, if it were possible to do.
But to me, updating with beta drivers and what have you is part of the fun of being at the cutting edge of technology!