I think I'll stir up some heat here, but I'd like to make it clear that it's not towards the original poster, nor anyone other particular person. It's just a general observation.
My take on this lens is that it'll generate a legion of lazy photographers. When up against a tall building, most will just frame, shift up and move on with life, forgetting about any possible connection – or exploratory research – between photographer, camera and the said building. From the samples I've soon so far, which are far too few to draw any conclusion, this has been recurring. Camera placement, especially camera height, plays an enormous role in the outcome. It can be forgotten – or overlooked – by this frame-it-all lens. With 4x5, you have to be damn sure that you've got the desired picture, and that means searching for the best camera placement. On the other hand, with a DSLR and a very wide-angle shift lens it's easy to get carried away. It already happens with the current 24mm TS-E, and will get worse with the newcomer.
I know the 17mm TS-E has its applications; as a 4x5 architectural shooter, my 75mm lens (19mm equiv.) gets much love. But it also taught me to use it sparingly, only when the situation demands it. I much prefer to use it with 6x9 roll film; or better yet, a 150mm lens on 4x5. It took me a while to move away from wide-angle lenses to more normal focal lengths (~38mm equiv.) when shooting architecture, and it's been a pleasure to do so. But that, of course, is personal preference.
That said: Canon, now it's time for a 35mm TS-E.