I like this lens a lot. I bought an older version of it on eBay which does focus rather slowly but you have a handy focusing distance limiter which helps a lot. The lens is amazingly sharp in the whole aperture range. I also used it a lot with a 1.4x extender and liked the results. I wish the lens wasn't so heavy and bulky but it's a 300mm lens so may be I want too much.

Have the older AF version....excellent value. About as sharp as the AF-S version, and compared side by side with the 300mm f/2.8 AFS (I) which I also owned for awhile, it looses, but by 50 yards, not by a mile. It is the only 300mm svelte enough to easily fit in a normal camera bag (assuming the bag is high enough) and with an 80-200 and a couple of extenders makes an exceptional long range kit for nature work. It's a little slow to be ideal for sports, but can be used reasonably well if you are an amateur sports shooter. Finally, it actuall works with the 2X Kenko Pro 300 in autofocus mode if there is good light. In general, this ain't supposed to happen, and on other of my lenses, past or present, it doesn't. But it does with the 300mm f/4 AF. One of the real bargains in my kit.