This is a REALLY nice lens.
I've used it in Canon fit, and its as good as the 150mm IMHO.
Its really quite a lot bigger than the 150mm and while the 150mm isn't that easy to handhold (due to weight and focal length), with the 180mm you will need to be on a tripod all the time.
On a Canon 30D with a 1.4x TC you can't AF either for some reason (probably fine in Nikon land)
So while this is a great price, don't buy it just because its a good price - consider if you will be able to manage a 180mm macro. It's large enough that you wouldn't carry it casually, whereas you can with the 150mm.