First of all, be careful with the reviews - some of them look for a perfect lens and that is a tough spot to start from (i.e. highlighting all the bad).
My sister-in-law took her 18-200 to Africa and absolutely loved it for landscapes and people shots (she also had a 70-300 VR for safari purposes).
Regarding changing lenses while travelling, is not really not a big deal, just have a CCD cleaner with you to remove the occasional (and I mean occasional) dust particle.
Regarding the 18-105, I am not a big fan of Rockwell, so I avoid his site all together. Thom Hogan has quite a few reviews on his site -- he is very candid about lenses, but also looks at "bang-for-buck" (i.e. value)
Here's his review:
http://www.bythom.com/Nikkor18-105lensreview.htm
He also has some articles dedicated to lens combinations (e.g. which lenses he would travel with in particular situations:
http://www.bythom.com/DigRecs.htm)
You might want to check this site as well - it has some of the most in-depth lens tests I have seen:
http://www.naturfotograf.com/lens_surv.html
You might also want to look at NikonLinks (
www.nikonlinks.com) for more reviews...
Hope that helps...