I bought this (expensive) lens only recently but after almost 5.000 shots I think I can tell a bit more about the lens.
It is a great beast and easy to work with. It weighs about 3.2 kg and could be handheld as well due to the excellent VR. To be honest I should buy a tripod or good monopod to work with it, but I am simple not a tripod lover and I can handle this thing easily. My 70-200VR lens seems a toy after using the heavier 200-400/4 VR for a long time.
The colorrendering as well as bokeh are wonderfull. Even in low contrast situations the lens produces high quality images.
I am very pleased with it and would recommend this one to everyone (budget permitting ofcourse)
I also used the lens with the 1.4 as well as the 1.7 converter. Not too happy with 1.7 under lower light circumstances and the lens is somewhat slower with the 1.4 converter, but I mostly use the lens with the 1.4 converter to be honest.