I've used Ubuntu on four different brands, that were mine, and a couple of installs for people. The buttons worked fine.
My own machines:
IBM T43i -volume, brightness, LED light and network disable
Dell Studio 1537 -Volume, web browser, brightness, CD eject, sleep, media player.
Acer 4250 -Volume, brightness, media player, network disable
Toshiba C655D -Volume, brightness and network disable
Compaq Armada M7000 -Volume, brightness
The only thing I never could make work on any of these machines was the finger print reader on the Dell. I found an app that was supposed to work but, I was going to have to write some code to make it work.