From everything I've been reading, it took quite a while to work most of the non-working feature and compatibility (for most games) problems for the 8500 out. As for performance issues, I'd say both of the major companies in question here usually take a few months after initial release of the hardware before the true performance potential starts to be realized in the drivers. But all of my nVidia cards so far seem to have all the promised features working out of the box, and practically every game works fine right away. Performance wise, there were usually increases later, allowing each card to finally stand out from its predecessor by a noticable margin (GF2Ultra - GF3, for example).
I got an 8500 the last year about 3/4 weeks after they came out. Right around Thanksgiving. I installed it fresh on a Win2k PC and since then I have not had one major issue with the card. Shure there were some bugs that got worked out (for example flashing texture in C&C Renagade). The very same day I got it, they had released their first beta drivers which fixes the Q3 issue and had working smoothvision. So for me, its been a very smooth ride. I realize that I might have gotten lucky.
For features that were not working, we had smoothvision only. And that was fixed with their first set of drivers. There was some talk about OpenGL and HperZ2 but at the time it was really hard to figure out if it was working or not. It was working fine in D3D.
If anything we can learn that ATI has vastly improved thier drivers and I doubt we will see the same thing again. Also not every NV card had good drivers. Do you remember the GF3 first reviews? Remember how nV ask to hold back the FPS numbers for a month? Also HOS support has been turned on/off in their drivers. At one time they had advertise that the GF3 can do it.
I hope ATI has learned its lesson as that will make better stuff for us all.....