Hello again to any folks who were following this thread...
I've been trying out the Nikon 180mm and just wanted to offer this review:
The optics are terrific, the image quality being lovely even at 2.8. The difference in sharpness between 2.8 and 4 or 5.6 is minimal, although I can tell you that the lens is at its best when stopped to 4 and beyond. The colors are accurate and look rich and contrasty straight out of the camera. I'm actually shocked by this. Nikon glass, when it's good, is very very very good! Huzzah! Too bad the bastards don't have the lens selection that Canon does! They make me mad and drive me to bad writing with plenty of these: !!!!!!
Moving on: if your birdfriend isn't moving too rapidly, the autofocus performance is actually quite good, even with a D90, but the autofocus falls apart when you're trying to snap fast-moving creatures like...wait for it...birds! I would hazard this guess: the autofocus performance would be quite a bit better with a D300 or D7000, etc etc.
The other big problem is that to switch to MF (which is something I want to do quite often, especially when the AF of this lens goes a-hunting) you must flip the switch on the lens AND on the camera too! A royal pain in the posterior!
That said, the lens is a joy to hold, its construction is top-notch, and it's quite easy for handholding...
Now, don't get me wrong: $1000 is a lot of money, but the optics here are as good (or better) than some Nikon glass that costs twice the money! Or even more than that!
I don't imagine I'll buy this lens but it's very nice to use for a little while...
All the best,
David