I put my name on the list at Roberts Imaging to buy the Nikon 16-35/f4 VR lens as soon as it hits the store! I certainly could use it with my D300, but I already have the 12-24DX/f4 and it is my favorite landscape lens. But, I'll be buying either a Nikon D700, or if announced maybe a D700s or even the rumored D900 (24.5MP), and then I will want (not need) the 16-35/4VR. Yes, I could use my DX 12-24/4 on the D700 either in DX mode or in FX mode from 17-24 without any problem......so there is not much of a reason to switch (please don't tell my wife I said this). My 12-24/4 is a small lens, but an absolute gem. The new 16-35/4 is a monster. So it will pair with "The Beast", my Nikon 28-70/f2.8. The 16-35/4 weighs 24 ounces, 3.2" diameter and 4.9" long. I love my D300 & 12-24/4, and have absolutely not one valid reason to make this change. I'll sell both of these once I have my new toys though. I've tried having two bodies but never carried both, so that's not an option.