I had in my D90 18-105 a standard lens case, and wanted a slightly larger telephoto range. I am extremely pleased with the 18-200, is as sharp as the 18-105, only slightly heavier, perfectly finished, and I am satisfied with the images in any way.
The Nikon 18-300 was too large or heavy, the Tamron 18-270 I returned thanks to Amazon after 3 weeks again, because it just could not keep up with the Nikon-original.