Use the 186.18 drivers. This fixed my micro-stuttering issue almost entirely.
However, this is restricted to GTX 200 series and lower since this version is pretty old...
But Fallout 3 had the exact same stuttering problem with the newer drivers going beyond 180s.
So use 186.18 along with the d3d9.dll hot-fix until either Nvidia or Bethesda gives us an official fix.

I have a GTX260 and changing the water multisampling to low also seemed to help, but you probably already did that as well.