Hi, I bought the 14-24 about 18 months ago. It is very sharp and very useful for architecture. It suffers from distortion, though .
Although LR4 corrects this automatoically, you loose quite a lot to the resulting crop and slao some sharpnes due to the resulting interpolation.
I have gone back to use my old 18mm MF lens a lot, is also works very nicely ( you will spot two shots in my gallery) the advantage is that you CAN use a 72mm filter to potect the lens, it fits in your trouser pocket and it is quite easy to do hand - held night shots. And you never need to worry about sand or humidity in the tropical forest.
If you really do a lot of architecture ( I di jobs for a real estate agent) buy the 14-24. Don't be led to think you need it for landscape, I find it too extreme.
Just had a look in LR: among among the 1500 shots I took with the lens, about 550 are taken at 14 mm, about 80 each at 15mm and 16mm.
90% are buildings inside out, a few are rainforest shots trying to include the canopy.
The 14mm has one big advantage: you can hold the camera parallel to the building and crop off all the superfluous stuff, as in pavement or floors.
For other purposes, get the MANUAL 15 or 18mm, no distortion, and the latter is really easy to lug around.