Is that still true in Nvidia's case? I originally bought an Nvidia card because of the supposed Linux-friendliness, but it's been giving me trouble.
Sorry to hear that, try another driver, an older one if necessary. I have a multitude of nVidia cards, and they all work right if you pin down the right driver. I have 6150 LE onboard in nForce-chipset boards, I have a Quadro 295 NVS in an HP C2D I just bought, might upgrade it to a C2Q for $50, really slick low-power setup there with support for CUDA 6.5 anyway, not too bad. 240GT, 450GTS OC, 750 Ti. Seriously all working great under Linux, but seriously none of them using the suggested driver.
I keep hearing stories about nVidia driver being hard to install manually but I'm doing Linux From Scratch right now (I'm currently starting over after a successful LFS 7.7 build now that I'm educated, and combining CLFS 3 and LFS 7.7 along with building with GCC 5.1 and multilib glibc 2.21, libressl, compiz...) and I've found that the nVidia driver still installs flawlessly on LFS just like it did on say Slack back when the nvidia driver was new. But like I said, you have to go driver hunting. For example the driver which comes with CUDA 6.5 won't build with a modern kernel and/or toolchain, so I had to hunt up a different driver (340.76) to support my NVS 295. And when I got my spanking new 240GT, it wasn't even officially supported by the driver yet but being 3/4 of a 250GTS it did actually work... as long as I installed the next-to-newest driver, and not the very newest one. Then another version or two later they added explicit support for my card.
On the other hand, I tend to try an ATI card every two or three GPUs, and I am always pissed off. I bought a gateway netbook with R690M chipset and that still isn't properly supported several years later. fglrx never supported it (said it was "too old") and radeon still trashes the display when used.
If you want proper Linux support, you're better off with nVidia. If you want open-source driver support for a moderately new card, you may be better off with ATI, but it depends on the specific GPU. If you want open-source driver support for a very new card, that's pretty much just Intel anyway.