I bought this lens to use on my D700. While it is quite small it is also surprisingly heavy, giving it a solid, quality feel. It is quite easy to achieve sharp focus down to f2 but a bit trickier at f1.2 and f1.4; I find I can get good results just judging it by eye and not needing the focus confirmation dots, although I suspect it would be a lot harder to focus on a cropped sensor camera and I'm not sure I would recommend this lens for users of cropped sensor cameras.
The lens is very versatile - it has a lovely soft look to the images at f1.2, but is bitingly sharp at f2. There is quite a bit of vignetting at these apertures but I like that look.
I know I am still in the honeymoon period with this lens but it is rarely off my camera, it's quality build make it a joy to hold and to use, it gives great results and is very versatile. Getting back into the way of manual focusing took a little bit of getting used to and I'm still not as quick as my auto focus lenses are but I don't miss auto focus when using this lens.
Thoroughly recommended for users of full frame cameras.