my computer: q6600 @ stock speed, been running 24/7 for like 6 years now (i bought it when it first came out), 4gb ram, 500gb hd, 40" 1980x1020 seiki tv/monitor & a 22" viewsonic side monitor & a 15" 4:3 old style lcd.
I forget what I had when I first got the computer, but I upgraded to a nvidia 9800gt because I got a good deal on it. That was really nice.
Then I decided to go for ATI, the 5770 was only $130 when it was released and I got a free game (which I never did play) so I decided to get it to be ready for Direct X 11. It wasn't really any faster, maybe a little. The picture quality was great and it overclocked very well, I could almost max the sliders on the ati thing and w/ it at %100 fan speed it actually ran cooler while overclocked. The overclocking didn't help too much but it gave me the few extra fps I needed to play smoothly in most things.
Well, it died (dunno why, I woke up from drinking one day and it just didn't work), so I bought a evga superclocked 560 1gb. I was expecting a huge jump in performance but again it doesn't really perform much better than the 5770 did. Not only that, but with the 5770 I could play a movie/tv show/cartoon on my second monitor while playing a video game and it never seemed to affect the performance at all. The 560 won't let me do that, the second monitor just goes black and the sound stops by the time the episode/show switches to the next episode.
I used to upgrade my computer all the time before I got the q6600, which has been one heck of a processor throughout the years. It's finally about time I replace it because some newer games like Planetside 2 just won't run worth a flip. I've had nvidia/ati cards both and never had any serious issues with either. I still have a number of rage/radeon/geforce cards in a drawer and they all still work as far as I know.
I never understood the disdain most people had for ATI as they've never really given me any issues performance or driver wise. When I do finally upgrade my computer I'm not sure which I will go with but I'm leaning towards an ATI board again.