nVidia's own control panel is not always very intuitive to use. Especially the 3D rendering settings are very cryptic and difficult to navigate. Even the new control panel introduced with the 9x.xx line of Forceware drivers isn't a real improvements for these problems. nHancer is a tool to improve the usage of these features.
There's a new final out of nHancer, which apparently addresses some important Forceware 185.xx issues.
But it's such a powerful and handy tool, even for the average guy. So another aspect of nHancer is to improve the handling of those profiles by adding many features that the normal control panel doesn't offer at all and improving the ones that it does offer.
Important notes This version requires .NET 3.5! and ONLY works with drivers from the 185 series or those > than (e.g. 185.66/68, 186.xx, etc.)