Just installed 12.04 and no wifi.
Settings => Settings Manager => Additional Drivers =>
Broadcom STA proprietary wireless driver
Tested by the Ubuntu developers
This package contains Broadcom 802.11 Linux STA wireless driverfor use with Broadcom's BCM4311-, BCM4312-, BCM4313-, BCM4321-,BCM4322-, BCM43224-, and BCM43225-, BCM43227- and BCM43228-basedhardware.
This driver is activated and currently in use.
This driver may well be activated, but it certainly isn't in use!
Clicking on the up/down arrow thingy on the top panel reveals:
Wired connection 1
Nothing there about wifi...
... Is it me? (btw, it worked 100% under Xubuntu 11.10)