One company that offers almost no support for Linux is Nvidia. If you want to use free software drivers for Nvidia you have to use Nouveau which ,until recently, Nvidia provided zero documentation for their hardware, so the nouveau team relies on reverse-engineering Nvidia's proprietary driver for Linux in order to write a free software driver for it. You can see Linus Torvalds frustration about Nvidia in this famous video: http://www.youtube.com/watch?v=IVpOyKCNZYw (Image removed from quote.)
Which is tragicomical since Nvidia is widely quoted as THE hardware selection for linux if you want problem free operation. The proprietary driver version has legendary fame in linux circuits but to be honest it didn't impress me. I saw basically no difference to the current AMD drivers in speed or support.
