After what seemed far too long a wait, Nikon finally got around to updating the 300mm f/4. The changes are not just cosmetic, but substantive in almost every way:
The lens now uses the AF-S silent wave motor. This means eerily silent focusing, with a bit more snap than before (read on).
The lens focuses substantially closer (5 feet [1.45m] instead of 8 feet [2.5m]), and has gained two additional elements (still in six groups, though).
The filter mechanism has changed from 39mm drop-in to Nikon's standard 77mm front thread.
The dreaded "put a sock on it" lens hood is gone, replaced by a standard 77mm cap.
The tripod socket has been grown considerably in size (read on, though).
The "girth" of the lens has been enhanced, making the diameter larger (though with little effect on weight), and increasing the size of the width of the focus ring.