OK, finally got around to purchasing PTGUI. I know some of you use it, and I was wondering how much processing you do in your raw processor before you try to stitch your photos
1. This has nothing to do with PTGui.
2. Generally you should do in the raw conversion everything, which is done best in the raw conversion; the following stitching does not change on that. Particularly, vignetting correction should be done in that stage.
3. Do only scene sharpening, and only moderately. I often generate a set with medium sharpening for picking the control points (I do this manually), and later a new set for the final pano.
4. Pick WB and change colority on all images together.
5. If possible, change contrast, saturation, brightness, recovery and curve adjustments on all images together. If you have to make individual adjustment, do it only moderately.
6. 4 and 5 above are under the assumption, that all frames have been shot with the same exposure and ISO, and the illumination did not change during shooting the frames. If this is not the case, then a tiresome process follows: adjusting the frames, so that the brightnesses match.