This is an amazing lens - if you have read any of my other reviews, you will see I only speak about lenses I own or have owned.
This is perfect on a full frame body (no crop factor) as you wil get the full use out of it's DOF control (larger sensor allows for shallower DOF - this is why compacts have difficulty isolating subjects - tiny sensors). I use this on my D700, it is probably my favourite tool in the bag save for the 85mm f/1.4D. If you want a lens to take some snapshots of your son or daughter, walk away and spend your money on a £300 50mm f/1.4G or an 85mm f/1.8D - both these lenses will get you amazing pictures if you know what you are doing. However, if you want to take portraits to the next level and give them a look that really few lenses on the planet can match - buy this. This, along with the monster 200mm f/2 (too heavy and too long IMO), are the go to portrait lenses.
This lens has DC - basically bokeh control or out of focus control - for the foreground or rear of the photo. These effects are subtle and you will only see them later on on the pc, not via the viewfinder. The lens also functions as a soft focus lens if you put the DC ring number higher than the aperture, perfect for female portraits in some circumstances. If you want sharpness, you need to put the DC ring to the same as you aperture, e.g. if I was shooting at f/2 I would put the DC ring to f/2 REAR. But it doesn't stop there, there are lots of configurations. When you buy it you may find alot of f2 pictures are out of focus, especially for tight headshots. You have very limited DOF at these distances (a good thing generally but AF is hard to master). I sometimes manual focus if I am really close, rest of the time I leave it on autofocus mostly. This lenses long focal length of 135 and fast aperture means most of the time if your subject is near-ish to you, you will be able to totally blow out that background and isolate them. It's fantastic for set up or candid portraits.
The lens has quick AF - but needs mastering and in some types of lighting you will need to switch to manual. I do not have a problem with this. It is built like a tank, from a by-gone era that we may never see again. When the world used metal instead of plastic and built stuff to last a lifetime. It's not water sealed so don't go swimming with it and be careful. The lens hood is awesome - Nikon should bring this stuff back, I hate these plastic reverse hoods we get nowadays. This extends out for shooting and folds back up!
It's expensive - of course it is. But it's going to last you a lifetime. Also another point worth mentioning - do you really think this lens will be about new forever? I doubt it. Nikon will discontinue this just like they did the awesome 28mm f/1.4 and the price will skyrocket. Even so, I doubt I'll sell it. Beware when you buy this, don't expect to shoot like a pro right away with it. Patience young jedi...