Hi spotmeter (what a name),
if you go with the Canon TS-E 24, I would highly recommend to invest $ 25 in PT-Lens (http://www.epaperpress.com/ptlens/index.html
). It is the only software correction tool for shifted images I know of. I use it always with images from the TS-E 24, TS-E 45 and the Olympus PC 35. It really improves the images (distorsion, ca and vignetting). The only thing you have to do by hand is to remove magenta lines at very contrasty edges. With this combination I photographed over 300 high-rise buildings and other architecture. Nobody complained so far in terms of image quality.
I would invest in the enlarging (2x) angle viewfinder too. Even with a building 20-50 meters away focusing is critical. Setting the lens to infinity doesn't give optimal sharpness. As far as I know infinity on the lens barrel is "beond" infinity because of the tilt capability. Perhaps live view solves the focusing issues - I worked for the last few years with the EOS 1Ds Mark 2 without live view. BUT accurate focusing is even with the 24 mm lens necessary.
If I shift more than 5 mm I use f11 instead of f8. The reason: f8 gives the best "center" sharpnes. But at f11 the corners still improve. The center gets a bit weaker, but over all the image looks more consistent. But still center sharpness is better than corner sharpness but it differs less.
Last hint: Check and double-check that the tilt is set to zero! That gives you also unsharp and distorted images.
In my opinion the lens is often rated so bad, because it isn't used properly. I hate the lens because it forces me to do so much post production, I love this lens because it gave me already so many good images. I look very jealous to the Hasselblad TS 1.5 thing because it records tilt and shift into exif and does an automatic correction. But what is the price for that, uhh.
Hope that helps