So, just for the googles: if you’re considering upgrading from Ubuntu 9.04 to Ubuntu 9.10 or 10.4 and you have a Broadcom Wireless adapter of the 43xx vintage (mine is a 4312) I believe this advice applies to most of them.
You should, before doing anything else, open a terminal, change your sources list located at /etc/apt/sources.list manually (globally replacing “jaunty” with “karmic” or “lucid” for 9.10 or 10.4 respectively) do an “apt-get update” and then install the b43-fwcutter package. Yes, the one you didn’t need before and won’t be informed that you need now. Otherwise you’ll find out that your wireless connection doesn’t work when you reboot post-upgrade. You should then pause, take a breath, and look forward in breathless anticipation to the day that “apt-get dist-upgrade” isn’t synonymous with “Russian Device Driver Roulette”, and know that we are of one mind on this.
But hey, it’s only 2010.
Yes, yes, I know I should know by now. Screw you guys.