Originally posted by Nutty
No, what he means is, the developers probably use nvidia cards as their primary work machines. They then test on other cards to make sure it works okay. But initial testing, research, and getting things right are done on their cards.
As JC said, the majority of his work on doom3 was done using an nvidia card in his work machine.
JC also said that a year ago and considering his OpenGL stance that's certainly reasonable. However, a lot has changed in that past year:
1) ATi beat Nvidia to market with a DX9 part by over six months and have given quite a few 9700 boards to developers
2) ATi's drivers have continued to improve by quite a bit.
I still think it's fairly safe to say that Nvidia holds a plurality of developer support, though.