For the most part, this is a lens that you will probably end up renting a few times before knowing if you will want to buy it. It is one of the more expensive ones on this list, and it is different in that there is very little vertical distortion in the corners. Horizontally, there is some stretching, but for architecture, landscape and other wide angle shots it is really quite a spectacular lens.
Im finding that I use it most when going for wide shots underwater and with the steadi-cam. Again, this is a very niche lens that will be one of the last you will add to your collection.