I bought this lens for Astrophotography, this was the best decision I have ever made apart from purchasing the 6D. Compared tot he 14mm, this lens is so much sharper and faster, and for night-caps the images it captures are just beautiful. Star diffraction is nice when stopped down, as well as tars get VERY sharp when stopped down to ƒ2.8-3.5.
Portraits can be a lot of fun with this lens at ƒ1.4, but you will need a good focussing screen – I recommend the Canon EG-S screen.
Landscapes are super easy on a walkabout, just set the focus to infinity, aperture to ƒ5.6 and snap away on AV mode.
Astrophotography, this lens beats everything hands down (my opinion) have a look at my Flickr account and make your own minds up.

