(ok, this is slightly unfair to intel's video drivers, they work fine as long as you don't need 3D acceleration)
You can make the argument that nVidia Linux drivers are much better, but I don't see where you're getting the idea that it's hard to find AMD drivers.
The closed AMD driver is pathetically bad. Neither multi-monitor mode works for me in Gnome3, due to from what I gather is AMD not keeping up well with architecture changes. AMD is also dropping support for their oldest architecture in their next driver release, leaving a ton of cards - some still being sold today - with nothing but the open source driver anyway.
My next video card is going to be an Nvidia for sure. Whatever Nvidia's faults, their proprietary linux support cannot possibly be as poor as AMD's.
And yes, I did. I actually spent half a dozen hours fiddling with xorg.conf etc trying to get multiple monitors to work with fglrx [AMD proprietary driver]. I should have known better. Especially since my not-that-old card is being dropped in the next fglrx anyway.