It is an interesting new development, going beyond the focal lengths of the Nikon 120–300 constant aperture f 2.8 and Nikon 180–400 with built-in TC constant aperture f4.
I appreciate some Nikon users object to leaving an FTZ permanently attached to one of the Nikon options, though either lens is more recent optical design than Nikon Z mount introduction.
With the FTZ attached to the 180–400 the weight increases is minimal, and it still fits in the Nikon shoulder bag with a Z8 or Z9 attached.
Whether the new lens stabilisation system is fully compatible with Nikon is something that has not been disclosed.
I am not keen on the thumb screw lens hood securing method – the new click and twist method with Nikon Z lenses like the 800mm f6.3 I consider far superior.
The launch price of the new lens seems approximately half the UK street price of the two Nikon shorter focal length lens options.
Whether we will see a Nikon 300–600 f4 with built in TC is for the future. I speculate some would buy this possible future combination
Addendum - Nikon are maybe being pipped at the post with this new lens for video.
The reference to a variable neutral identity drop in filter can be important for video.
Often 60 fps is fast for video - and the shutter speed should not normally be more than twice the fps - limiting shutter speed to 1/125 in bright sunlight.