Rather than being a "preview driver" like AMD's, this release comes with certification from Microsoft's Windows Hardware Quality Labs. Nvidia claims the drivers support OpenGL 4.0 "fully" on GeForce GTX 470 and 480 GPUs, at the same time ushering in OpenGL 3.3 support on "all other G80-based GPUs or higher." That means anything in the GeForce 8 lineup or newer, including integrated graphics chipsets.
AMD's preview driver also supports OpenGL 3.3 on cards as far back as the old Radeon HD 2000 series.
Whether you're talking about AMD or Nvidia, though, neither firm seems to taken too long rolling out drivers. The Khronos Group only released the OpenGL 3.3 and 4.0 specifications a month ago. Features in the OpenGL 4.0 programming interface include the ability to offload tessellation calculations to the GPU, performance improvements, and much more. See our coverage for additional specifics.
You can grab the Nvidia driver from this page for Windows 7, Vista, and XP in their 32-bit and 64-bit iterations, not to mention Linux, Solaris, and FreeBSD. (We assume those non-Windows releases don't have WHQL certification, though.)