I have a Hartblei Super Rotator 80mm f2.8 and use it mainly for equipment shots to achieve correct perspective and also to obtain total depth of field control where the tilt aspect has particular importance. Basically a tilt and shift mechanism like the Super Rotator mount is like using a view camera with all movements, except that you cannot tilt the film plane with an SLR.
Here is the lens itself and also mounted on my old istD.
Using just shift lenses, i.e. the shift part of tilt & shift, with wide angle lenses was used pre-digital to correct for converging verticals, but with the advent of digital, especially with APS-C, wide angle tilt lenses would have to be around 18 - 21mm to be of much practical use and is of no real benefit.
Here is an example of using perspective correction in software using a normal lens (DA 16-45 at ):
The uncorrected shot:
The corrected shot, done in PS CS2:
I often do mild perspective correction in my Raw converter (SilkyPix) rather than PS, as it has better controls and seems to destroy the image less, here is an example:
Full shot DA 16-45 at 16mm:
PC corrected shot in Silkypix, as it was shot non centre to the building I didn't want to correct for the horizontal, but could have done so, but it lost some of the feeling, being too "sqaure on":
But using tilt enables the whole subject matter from near to infinity to be "in focus" even with wide apertures. Here is a very rough example:
No tilt or shift, you can see the plane of focus is horizontal across the frame by looking at the woodgrain on the desk, and the camera is out of focus on both the left and right hand sides:
With tilt and shift, you can see that the plane of focus is tilted and runs across the face of the camera and most of the camera is now in focus, even using an f2.8 aperture:
I did say it was a rough example! I don't have better examples on my site at the moment, but I trust these will suffice.
You can read up on the effect of T&S lenses by doing a google for tilt and shift, perspective control and schleimpflug effect.
Have fun!
Cheers