To coincide with the GeForce GTX 780 launch, Nvidia has posted a set of graphics drivers with support for the card. The 320.18 release boasts certification from Microsoft's Windows Hardware Quality Labs, and you can download it in 32-bit and 64-bit flavors for Windows 8, 7, and Vista.
Judging by the official release notes (PDF), there isn't much new going on in these drivers besides GeForce GTX 780 support.
Nvidia mentions a couple of bug fixes: one that lifts a 999MHz clock speed limit on Fermi-class graphics processors, and another that prevents X-Plane 10 from hanging when it loads. Other than that, it looks like users can expect the same tweaks and optimizations as in the 320.14 betas, which themselves inherited a wealth of performance optimizations from the 320.00 betas.
Compared to the previous WHQL release, which was numbered 314.22, the 320.00 betas brought about single- and double-digit speedups in games like Assassin's Creed III, Battlefield 3, Far Cry 3, StarCraft II, and Tomb Raider. Nvidia outlined the performance gains in detail in this article on GeForce.com. (Thanks to TR reader SH SOTN for the heads up.)