I completely agree with Randall. I used one on my D200 and my son's D90 with very nice results. It was my go to travel lens, and seemed to be the lens that was always on the camera. If I had something specific in mind to shoot, I would go to a prime, but when I went out shooting with no specific objective in mind the 18-200 was it.
It took me a while to find the best way to use the lens, but eventually I just set it at f/8 and went about my business. Many sharp photos resulted. The only limitations I found were that at the 200 end it was not quite as good, and when traveling in Europe, it wasn't wide enough to suit me. So I usually carried a 12-24 in addition. The only other negative I found was the extreme extension of the lens was intimidating to people I was photographing. I think it may have cost me a few casual travel portraits, when people would shake their head or hands indicating "no photo" when I zoomed it out to near 200mm. I traded mine to Mick Klass as part of a D700 deal, but wound up buying a 24-120 f/4 for my FX travel lens. It's great!