About the 18-200mm VR lens, I think for the great landscape and nature shots you take while hiking up mountains, it is a good lens still, as its weight/size to performance ratio is good. The 80-200mm is much heavier and larger. I had to buy a new Lowepro backpack style carrying case just to be able to bring it around town. I don’t think I’d ever take it up a mountain, unless it was an easy-ish day hike. I was able to carry my D80 and 18-200mm fairly easily up Akadake (2,899m) recently, but I don’t know if I would have dared to bring the beast 80-200mm on that hike. But no doubt you are a much stronger hiker than I am, so maybe the extra weight may not matter.

But yeah, sharpness was also one of my concerns, but maybe even more was the vignetting at the 200mm focal length. I have started to print out selected shots at larger than A4 size and then I really noticed some darker corners on a few shots.

Let me know if you get the 80-200mm. If you don’t mind spending more, getting the AF-S 80-200mm would be better, as the one weakness of the AF 80-200mm is that it doesn’t focus quite as quickly as I’d like in some situations as it lacks the internal focusing motor (in Nikon’s nomenclature AF-S lenses have the silent wave motor to help focusing, which the 18-200mm does).