Optical quality wise, i dun think there are any noticable difference (unless u take identical photos and TRY compare them side by side)... its not like u r comparing kit lens with Lica lens.. :bsmilie:
I've just seen some photos shot with 18~200VR from another thread.. seems to exhibit the exact same problems I have in my 18~135 kit lens.
But if you look at flexibility, 18~200VR surely superior to 18~135mm, and 18~135mm is better then 18~70mm.
My 0.2 cents worth..