An article/excerpt from Aaland's Photoshop CS2 RAW book has been posted at webreference.com, and discusses at length how to reduce noise, correct chromatic aberrations and control vignetting in RAW files.
"With varying degrees, all digital cameras produce images with electronic noise, chromatic aberrations, and vignetting. Electronic noise shows up as extraneous pixels sprinkled throughout an image. Chromatic aberrations appear in transitional tonal areas as colored halos, color banding, or purple fringing (especially around backlit edges). Vignetting--darkening around image edges--occurs with a filter/lens/sensor mismatch. In this chapter, I'll cover how you can reduce the effects of these imperfections in your RAW files."