So, now it's time to resort to extreme measures to see if we can save this picture, or at least some crops from it. If you haven't read the background, look at the posts here. The stitching software (AutoPano Giga) has a plug-in tool that allows you to apply an Adobe Lens Correction profile to all of the pictures before stitching. You need a lens profile, and I found the profile downloader here. Vignette correction is tricky, as it will vary depending on the camera, lens, aperture, focal length and even image format. Adobe hosts a community where members can upload lens correction profiles and there are a lot of good ones out there, but finding the one that matches your particular shoot is hit or miss. I'm using a filter for the D700, with my lens and focal length, with reasonable success. So it's a simple 6 step process: pair down the panorama down to 3 layers, pre-process all 255 images, then control point detection, adjust the HDR merge parameters, render the pano and finally about 4 hours of post in photoshop. The end result, I don't think this will ever make it to print in wide format, but there may be 1 or 2 mediocre crop's in there. You'll notice that I have chosen to publish in a spherical projection that is limited to the image height, this minimizes the impact of the remaining artifacts. I think it's to the point that most people will tell me "no one would notice those" out of politeness when I point out the vignette artifacts.
So far the biggest lesson I've learned is that it's best to avoid vignetting from the get go. I think I need to spend some time understanding the impact that my camera, it's vignette correction, lens, aperture, ISO, focal length and image format have on the it. When I get some free time, on a blue-sky day I think I'll go shoot a series of 9 x 9 tests at various settings and see what it yields.