To follow up -

My two TITANs from ASUS do 1.0Ghz out of the box on air. I get the feeling that more performance is possible for SLI via driver updates, however they still rock 5760x1200. I hope they are not so rare a setup that NVIDIA spends some more time optimizing SLI.

Games that would stutter with 2x GTX 680s no longer do - however it still feels like more could be squeezed out of these monsters. Very happy with the out of box overclocks!