NVIDIA has today expanded their GeForce 600 series Kepler line-up with the launch of the GeForce GTX 670.
The NVIDIA GeForce GTX 670 is a $400 USD graphics card that like it's bigger sibblings -- the GTX 680 and GTX 690 -- is based upon a GK104 Kepler core. There's 1344 CUDA cores, 112 texture units, 32 ROPs, a 915 MHz core clock, 980MHz boost clock, 2GB of 6GHz GDDR5 video memory on a 256-bit bus. The GK104 is manufactured on a 28nm TSMC process and this GTX 670 is expected to burn up to 170 Watts.
As far as the Linux support goes for the GeForce GTX 670, it's presumably just like the other GeForce 600 series hardware.
When using the binary NVIDIA Linux graphics driver, it should already "just work" if using the latest binary blob. NVIDIA will presumably officially advertise GeForce GTX 670 support in an imminent beta/stable Linux driver update. The only limitation of the Kepler hardware on the NVIDIA proprietary driver is no overclocking support. For additional Kepler Linux performance information, see the Phoronix NVIDIA GeForce GTX 680 Linux review
On the open-source side, there is limited Kepler support
. If extracting the FUC microcode for the GK104 GPU by first loading the NVIDIA binary driver and playing with the Linux kernel's MMIOtrace, it's possible to already bring up OpenGL support for the 600 series on the reverse-engineered open-source NVIDIA driver. Besides the temporary microcode/firmware headache, there isn't yet any support for re-clocking, fan management, and other issues that are similar to Fermi.
Your best bet now if using GeForce 600 series hardware under Linux is to use the binary driver for at least the next few months.
As far as how well the GeForce GTX 670 performs under Linux, that's a good question. I don't have access to any GTX 670 hardware right now, and I probably won't, since NVIDIA PR seems to hate Linux
For now at least with OpenBenchmarking.org
's Cekora Engine you can find (Windows-based) GeForce GTX 670 reviews