I've been offline for over a week now, and it's not as bad as I expected. I have a 3G dongle but made the mistake of logging out in Dalaran, and can't zone in before it disconnects. I'm sure the lag would have made it terrible, but I was planning to jump online, blow a titansteel cooldown and log off. That isn't happening.
Broadband SHOULD be at the new place by the 24th, so fingers crossed it is.