Never had a good ATI. MY Nvidia chips have always been extremely reliable in normal or overclocking use and even after overclocking too fast it still handled it (with some purple dots all over my screen) and didnt break.
Nearly all of my friends that nought ATI's had issues and usually with our evenly matched machines, my NVIDIA outperformed.
Many, many other factors go into making a chipset good or bad though. I could suck out all the RAM from your computers or decrease a pipeline here or there and youd think it sucks