A very good lens but with some limits.
After years of using(and abusing) the original 120-300 f 2.8 HSM lens bought for about half the price, I was expecting a revolutionary difference in image quality. And for the most part, I am pleasantly surprised with my purchase of this beast.
On first inspection, it's bigger and heavier than the original. It has a smoother surface different than the old style which I think will scratch easier but after only a few weeks, I can't make that assessment just yet. The actual look of the lens has a "newer" style to it, like you are using a pro lens and not some 3rd party variable, slow lens.
A couple of things that concern me, which I had trouble in past with the old style was the collar mount. I went through a couple TS-21 collar mounts after the 1/4 thread stripped out rendering the collar useless. This lens is heavy and I see no way to remove the collar if this ever gets stripped unless you send it back for service. So everyday when I put this on, I tighten just enough to hold the weight. Another thing is the lens hood. The old style had a screw lock nut, this has a bayonet mount which feels kinda cheesy. After two days of normal use I already felt this loosen on me. I guess with the additional lens weight, they decided to save a few grams on the hood. Might have to carry some gaffers tape some day.
As far actually using the lens, the zoom and the focus rings are a bit tight to spin and I'm hoping after a few weeks this might feel a bit more normal. I find myself occasionally spinning the focus ring hoping it will loosen.
The autofocus is dead on and quick. I used to micro adjust for back focus on the old one and I'm really happy after multiple tests that this passed with flying colors.
It's acturate but with limitations. I shoot mostly wide open @ f 2.8 and the DOF is feather thin. I mean really thin! With a 1.4 converter on, focusing on second base, you'll have the shortstop in focus and the base runner out. Some of the early football images this season got trashed because I focused on the jersey number and the face was soft. You really gotta pay attention to you focus points.
Focus tracking compared to the old style seems a bit slower in some cases. On certain situations where you pan and track horizontally, it holds pretty well. In cases where the subject is coming straight at you, it kinda locks in and holds the first focal point. I've been using the focus button on the camera to adjust focus to speed things up a bit. I've also slowed the frame rate down to 9fps. My D3 cameras are set with no lock-on and continuously focusing using the shutter button to activate focus. Again I'm hoping it's just "too new" and will break in.
Some of the vignetting on the long side is a bit more noticeable than the old style but is controllable through post editing. The bokeh is alot different than the old style. Much smoother and creamier. The separation from the subject to the background is well defined. It has a professional "look" to it. When I use a 1.4 converter the background just melts away.
A cool feature I never thought I'd use is the Stabilization. You really can hand hold this beast with acceptable results. I wouldn't recommend it but in a pinch, you can pull off a needed image. It works and it's pretty silent. Nuff said.
Overall, this lens is an incredible lens and produces razor sharp files when used correctly. I use the 1.4 converter about 70% of the time wide open and I get amazing results. If you expect to "spray and pray" all over a field, forget it.
Unlike most AF-S Nikkor's shooting sports(or Canon's), this requires a bit more effort to lock on and hold a player. And for a big difference in price, it's expected. But not by much.