i am planing to buy a new graphics card ... I 've knew the problem of ati drivers...And i 've heard that ati made knew drives they fixed the problem?

if you have to ask , then you have not researched it.
Nvidia for linux

ATI is coming along but they still have a long way to catch up to nvidia with open gl .

ATI has made some headway, but nVidia would be the better choice for Linux. There are also some folks who don't have nice things to say about THEIR drivers, too, but from my experience, nVidia works better in Linux.

Just my opinion...and worth every penny you paid for it.

ati has made a lot of headway with their drivers, as a general rule the nvidia cards have better support for all features. If you're not going to perform direct research I'd recommend a nvidia card, if you research you can find either side has ones that work poorly and ones that work exceptionally well.

Make sure you have a new ATI chip, which may well be 5000 series.

The rough cut with ATI is: support is improved and will be better in the autumn (probably kernel 2.6.36); They have a driver for the new cards and a slightly faster driver for older ones working more or less, (but rather less than more). Acceleration with ATI is a slow trot. Take GE, for example. I can't get decent zooming on GE, withj a twincore turion, whereas my old athlon single core 32bit running a nvidia mx-440 from the last millenium is miles faster running ge-4.2.

I have an r600; glxgears does 375FPS, using 99% cpu power, while X uses 46% (Yes, but it's a twin core). The other old box on nvidia does 2.2k fps with no significant X load.

This is a vote for nvidia. Hang out on phoronix.com to see what ati are saying.

NVIDIA.

ATI are playing catch-up.

My money goes to the people who supported linux from the early days (NVIDIA), and continue to do so.

It takes time . ATI was a MS ONLY shop for so long that now that they are not , it will take time for them .

Thank you...Nvidia is steel first and better

Nvidia here also. ATI is getting there but still not at nvidia's level.

Yup - NVidia is still first, and most definitely still better

If you want open-source, well-integrated, and unobtrusive, choose ATI.

Because of the wonderful open-source 3D driver!

It's still not perfect but it's 3D and it's open source!