Thinking more about it, this is the ultimate tool for many of our needs. Not only for nadirs/zeniths, but for moving objects inside shots bracketed for HDR too. Shadows and reflections in the mirrors etc, as well. The list of what it can be great for is long.
This fits in Photoshop so well. Let´s hope already CS5 has it implemented, that would be just perfect.
Wish I had this for the project I am working on right now. An oval spa dome with all the surrounding glasses reflecting the equipment in the middle of the spa pool. Ca 20 reflections to take out. Imagine the time saved by effectively being able to use PatchMatch.