Again a bit too late but well finally I've had time to refresh what's been missed. The GTX 670 is a very nice GPU. Reference pcb is amazingly short as for a card that performs that well but the cooler is bigger than the pcb since heat sink covers a lot of space on the GPU so there were no place to put the fan ant it sticks out behind the pcb. In case of performance it is close to GTX 680 and very very close to 7970. Yet it is very god in SLi too. 2-way sli has amazing scaling but 3-way sli is not so good right now. Maybe there is some kind of bottleneck or the drivers are immature. We'll see. The 7970 is better in power management since GTX 670 is not very power efficient at idle so that is the drawback of the new GTX 670. But anyway it is a very good GPU. It forced AMD to drop the prices of their gpu's significantly so we should see some interesting offers.
Single GTX 670: http://www.guru3d.com/article/geforce-gtx-670-review/2