Summary: The shift feature provides a limited degree of perspective control. Shift lenses allow to counteract the effect by tilting the lens off its horizontal axis. By doing so the projected image “rectangle” on the film or sensor plane gets distorted to a trapezoid which compensates the effect.
Summary: The TS function is limited on the original design. You have to check which item this is. But there's also a lot of price difference with the new II version (about 1000 USD). The lens is simply excellent. If you do not use the TS functions, it is probably the sharpest lens in this range.
Summary: This lens is great for capturing architecture and all inclusive scenes but not good to use as an all around lens. Auto focus does not work with this lens. This is a great lens as a third but I don't suggest buying it as your first or second lens.
Summary: Canon really earned their money with this lens! It is difficult and expensive to manufacture, and has a large aspherical lens as the front element for performance approaching apochromats. Version II of this lens has just been released, but it sells for twice the price.
Summary: I have had this lens for a few days. I ordered it since I was tired of stitching bad photos by hand, and finding everything out of alignment. I do mostly indoor and outdoor architecture, and nature scenes, so needed something with both a panoramic sweep, and to maintain parallelism in my subjects.
Summary: I had this lens for close to a year now, and have had many opportunities to use it. It's a great specialty lens if you frequently shoot what it is best at, and those type of shots are worth the money you spend on the lens.
Summary: I've used this lens on an EOS 1D Mk II at Bodie, California and for Anasazi ruins and petroglyphs in northern New Mexico. Its only big shortcoming is flare sensitivity, most evident in bright hotspots in the restored Great Kiva at Aztec Ruins National Monument.
Summary: Never used cameras bigger than 35mm so can't comment on the similarity to the large frame world. But I suppose if someone does come from the large frame world, using this lens would be a piece of cake anyway. I am a hobbyist and like to use this for tall buildings and large landscape.