Some of the critics in this thread have said "I'm happy you're happy with your 18-200, but I'm sticking with my 70-200 f2.8, which gives much better image quality." Fair enough. But it's not an "either-or" choice. Our cameras have interchangeable lenses so that we can use the best lens for the present purpose. Often, in my use, the best lens for the situation at hand is the 18-200.
I don't have a 70-200, but I do have an 80-200 f2.8 and several fast primes. And, I'll use them when the situation warrants. But sometimes the size-weight penalty of fast zooms, or the lack of versatility of primes, weighs toward a lens that may not be quite as good, but has the advantage of versatility and portability. Even though I have faster lenses with better image quality, I still use the 18-200 a lot, and the results look good to my eye.
The 18-200 isn't the best lens for anything, but it's a pretty good lens for everything.