One of the reasons why I will probably not buy an ATI/AMD (for graphics), is that support for older hardware is pretty terrible. I have an Asus laptop which worked *beautifully* in both Windows/Linux.
Apparently, some people (not me) had issues with brightness control not working on the fglrx driver. AMD fixes that, and on my laptop (and others, according to Google) the backlight breaks. As soon as X initializes my backlight goes dark. In a bright room I can barely see that X otherwise started successfully and is displaying a login window.. It's been over a year. I've seen lots of chatter on fixes for the brightness-control button, but pretty much zip about the broken backlight.
I can use the Radeon driver so that X will work, but video is choppy and since I'm working on actually developing GL code, it's pretty much useless for that. So... core i7 processor, lots of RAM, decently powerful GPU, and a farked video driver that renders the whole thing useless.
I had actually been migrating more towards AMD from nVidia since their graphics drivers had shown promise since ATI was acquired, but frankly the nightmare of bug-support is pushing me back towards nVidia. It especially sucks for a laptop since I can't exactly replace the GPU on what it otherwise fully functional hardware.
Currently I'm picking at firegl_public.c and related modules attempting to merge the 13.25 driver with the 8.960 driver (I've been told that reverting to the older driver will allow the backlight to work, but in my case it won't compile under DKMS).
To any AMD Linux driver devs listening: I would be happy to work with you on this. Hell, I can ship you the damn laptop for a few months if you believe that would help develop a driver that works again.