I actually grew up on an Commodore Amiga 2000. Played games that PCs and Macs at the time could only dream of. (circa 1987 - 1994).
My first computer was a cheap piece of crap thrown together with cheap parts, Pentium 200Mhz. Trident 2MB video card. Over time, i started replacing the parts with good ones until I finally upgraded the CPU and motherboard. In that new computer, I used the brand new Voodoo 3 2000. Freakin amazing card. Made the original game Unreal run like butter.
First card after that was the Radeon 8500. Another amazing card and was one of the first competitive Radeons (speedwise), however the kicker for me was 2d image quality. The Nvidia cards at the time just looked like Crap as they never focused on actual image quality, just raw speed. At this time, however, ATI's drivers were still pretty sucky as this was before the relase of the 'Catalyst' brand for their drivers.
Then came with Radeon 9800pro (no contest there for speed as Nvidia was trying to catch up from the FX mess). The ATI drivers were really starting to get really good, though the CCC was still horirbly slow as it relied on .net framework which isn't native to Windows XP.
Then the x800gto. This was basically me wanting to get a slightly better card that still worked in an AGP slot.
Then the Nvidia 8800gtx. This was when i built my current quad-core rig. Amazing card speedwise. Nothing could come close. But the decision to go quad core and Vista 64bit proved too much for the crappy Nvidia driver developers. I spent close to a year dealing with crashes, lock-ups, etc. 90% of those went away when i swapped out the 8800gtx with the Radeon 4850. The 8800gtx wasn't a bad card either. It was purely driver-related problems.
ATI did have some struggles making a good Vista driver as well, so i can't blame Nvidia completely, but when ATI was fixing bugs on a monthly basis and Nvidia let us 8800gtx owners sit for 7 months without a new driver update, I got pretty pissed off.
It does look like Nvidia has been focusing more attention on drivers within the last 6-8months and I have no problems switching back to them if their driver quality improves again, but until then, i'll stay with ATI.