I have the Nikon 28-300 on a D90. About a year ago I too was looking for a "all in one lens" this is not it on a FX body. On a bright sunny day this lens can produce some great shots, however it is a light eater. On a DX body you can up your ISO to compensate for the loss of light and the higher DX bodies can handle the higher ISO better than the FX bodies can. I don't think it's a good move.
If you really want one, and don't want to listen to our advise I could cut you a deal on the one I have, I'm almost willing to part with it. My lens arrived before my clear filter did and the first day I had the lens I scratched the protect coating on the lens near the outside rim with my lens cap. It does not show up in any of the images when used but cosmically it's there, I'll never get near out of it what I paid for it, not even used.
I watched this video about a year ago and here I am now writing this.
Nikon 28-300 Preview - YouTube