I'm an enthusiast. I had the Tamron 18-270 and returned it in anticipation of Nikon's 18-300mm. My intended use is specific. I'm going on an African safari. I did a similar wildlife-based trip to Antarctica and was constantly changing lenses because wildlife was sometimes popping up far away and other times popping up just a few feet away. There was no way to anticipate it. While on a game drive in Africa's dusty environment, constantly changing lenses won't be a good idea. I'd rather capture an image with some defects rather than miss the shot altogether. I know this lense will be big and heavy and $1000 is not a trivial amount of money, but it works for my intended use. I feel I didn't just buy a Nikon DSLR but bought into their lense system. All things being equal, I'll give Nikon lenses more consideration than Tamron/Sigma lenses whenever possible. I'd like to reserve critical judgment of this 18-300mm until it actually comes out and we can see how it performs.