As someone who owns both ATi and nVidia cards (4870, GTX 285), this is good news for everyone. Healthy competition benefits everyone. I'm still debating between purchasing the GTX 4xx and ATi 5xxx series next, but people continuing to report flashing graphics problems in some games with ATi drivers (as I did with the 4870) has me leaning nVidia.
Power consumption and heat are not a concern for me in a full tower ATX case. Hopefully they'll get whatever the problem is resolved before I make my final decision and pull the trigger this summer. But it is nice having that choice to make. I can't imagine how awful progress would be with nVidia out of the GPU business or ATi out of the business.