This machine is not hooked up the net yet. In fact, I have to install the wireless PCI card. I hope the drivers will work on Ubuntu.
That's going to depend on the hardware.
Here's a list of supported hardware...
And here's the definitive documentation on getting wireless to work on Ubuntu.
I have found that anything using the RT chipset "just works."
Edimax uses the RT chipset almost exclusively.
So that's all I buy.
As a bonus, Edimax tends to be rather inexpensive too.