[NFG]

I bought mine after reading a series of reviews that all said, basically, 'acceptable compromises considering the extreme range of the lens'. What I got was a lens that was never really sharp, never really had good contrast, and after I got some other good lenses (50mm 1.8, 10-17mm fisheye, 105mm VR) and trying out other lenses (Tamron 18-250) I came to the realization that it wasn't any kind of acceptable compromise: it was a crap lens with a lot of positive comments by less discriminating people.

The Tamron was so much better, smaller, lighter and cheaper that I consider the 18-200 VR an expensive mistake. I have since sold it to someone who thinks it's a great lens.

Try both, if you can. I know that if I hadn't gone full frame with the D700 I'd have picked up the Tamron for myself.