Picked this lens up two weeks ago and it blows me away - it's stunning!
I'm not a Nikon fanboy so I tried the Sigma versions (no Tamron or Tokina available in Dubai) but couldn't find a copy that was anywhere near as sharp, quick to focus or even accurate in focussing!
Tried the Nikon and it was no contest! Colours straight out of the camera are fantastic, it's very very sharp at f2.8 and then stellar from f4. 24mm is supposed to be its Achilles heel but it's still pretty damned good there (I'm commenting from a DX user's point of view) - obvioulsy there's barrel distortion but it is easily fixed in post if required. Here are a few examples. The first it hand held at 24mm and f2.8 (ISO1000) and the second and third is just to show is sharpness and depth of field (2nd is f8, 3rd is f2.