Dave,
Thank you for taking the trouble provide links and your personal experiences in such a detailed reply. You comment on the Kipon adapted is especially interesting. I certainly don't want to waste money, but am actually inclined to look seriously at what Mirex has to offer, if it is and actual tilt-shift adapter.
Their quality seems to be much better, and possibly worth the extra money IF I can find a decent ultrawide lens to mount on one.
erich