I've had this lens for a few weeks now and here are my first (amatuer) impressions.
Positives:
1. The lens works very well for macro shots.
2. Unlike what some reported here, it has great color rendition.
3. It produces very nice black and white images right out of the camera:
4. Overall, it is a nice walkaround lens. The focal length is great for most shots.
Negatives
1. The lens is not good in low light. I find I often have to shoot at ISO 1600 to get proper exposures, with a noticable amount of noise.
even before dusk:
Plus or minus--when opened up the DOF is VERY shallow with a small focal area.
I havn't had a chance to use it for daytime landscape shots yet. I am still deciding whether this or the 50mm 1.4 would be better for my upcoming trip.