I shoot architecture professionally and this lens mated with a 21MP full frame is a dream come true. I also use the lens for landscapes and panoramas, although, the 24 TS-E might be better suited for that application as it allows for front filter use, includes a lens hood and does not have the...
Nearly perfect even with large shift/tilt movements; The best architecture lens around, especially when mated with 21MP full frame bodies
The price but then again there's nothing else as good and if you shoot professionally it will easily pay for itself; Must use your hand to shade lens, which isn't a big deal since you need to use a tripod