One of the fun features of using a fisheye lens is its enormous distortion that disproportionally enlarges foreground elements. I own the Nikon 10.5 mm fisheye for DX cameras. After my wideangle was destroyed because of a car that drove over my backpack recently, I was forced to use it more often with my camera that had a defunctive commanddial because of the same incident. Also, since my new D300 included a license for Capture NX, I can now easily unwrap fisheye images. You can do this too for free with hugin, but this is much easier - just a single click. As an example here is my daughter taking a picture of me in Arizona with the fisheye:
I'm always amazed at the beautiful creamy skintones that this program and the in-camera jpeg engine gives. You have to work on this in other RAW converters (not just Lightroom). Anyway, here is the rectilinear projection.
Pretty cool. In this case, I think I prefer the fisheye image anyway, but it is a good illustration.