This is an old thread, I know, but it has some misguided information I'd like to address.
First, "shift" is 100% doable without a T/S lens, that is it is easy to get the verticals vertical, but you need to have a lens that is wide enough and you need to crop. So a shifted 24mm lens gives you a cropped field of view of a 17mm lens. That is, set up a shot on a tripod with a 24mm lens shifted, take it off and put a 17mm lens on your camera and a crop will exactly match the 24 image. The only important bit, and the reason for converging verticals, keep the camera level.
Second, you can do lens corrections for off centered T/S images, having said that the 24 and 17 are very well corrected for CA and off center vignetting is comparatively easy to correct with a software filter. Anyway all you need to do to do true corrections is increase your canvas size to allow for the shift used, position the image in the larger canvas to allow for the shift used then apply corrections, then crop back to the image. If you are anal enough you could even make actual lens profiles in the free Adobe Lens Profiler.