OK, I have some preliminary test results.
Between a careful reading of the manual and some actual testing on the unit it does appear that there is a pass through mode, which is achieved by setting the output resolution to the same as the input resolution. It appears to work that way, and the manual describes this as the "pass through mode".
It seems that at least a 1080I pass through works fine, and you can then apply the various aspect ratio corrections to the signal.
While I didn't have my lens set up to really look at picture quality, I can say that the addition of the scaler to the chain between my Toshiba HD A1 and my Panny 900 projector had no noticeable effect on the picture quality when set to 1080I in (this happens automatically as it senses the signal) and 1080I out set as the output resolution. (You might suggest using 720P for both, but I have it on 1080I mostly because of the very poor results for 720P output on the HD A1 before the firmware updates. After the updates I could notice no difference between the two settings, so I just left it at 1080I.)
After achieving the apparent pass through, I then experimented with the aspect ratio changes, and they all seemed to work as advertised. I looked mostly at the vertical zoom setting, and it did indeed stretch the picture vertically to fill the screen, and while the picture was now tall and skinny, it did not appear to have any other artifacts.
The next test will add the lens (Panamorph 380) into the mix, and I will give you my observations. If this one test, as well as testing the pillarbox function prove successful, then we will at least have a box that will provide the needed stretch for CIH, regardless of how it handles actually scaling and the many other corrective functions available on the box.
For me, the aspect ratio control alone is worth the price of admission, and any other benefit of the box is gravy.
By the way, it does look like it will pass through 1080P 60, as there is an output resolution selection for that. What is not present is any 1080P 24 support. I have nothing that offers a 1080P output in either 60 or 24 to test with.