As many others have stated, I bought this while waiting for my 18-200 VR to arrive. During that time I became attached to this lens. For professional work I ususally use one of my primes or my 80-200mm F/2.8D, but for walking around, candids, and some sports work, it's what I use most of the time.
I finally received my 18-200mm VR, so you might ask why I don't use the 18-200 instead. Unfortunately, I just don't see the advantage because with the 18-200 at the 18-24mm range I get a lot of CA, and at the 200mm range I get fuzzy images, so I ended up using the 18-200 mostly within the 24-180mm range. Well duh! My 24-120 practically covers that range with the same quality, and if I to push out to 200mm I use my 80-200mm or old 70-210mm for their sharper resolution. I've decided to sell the 18-200mmVR and buy a 12-24mm instead. I understand there is little or no CA using this lens, so I should be covered.
Bottom line if you want a versatile, quality telephoto lens the 24-120mm VR is a great deal. Buy it! It's at least as good if not better than the 18-200mm VR. One caveat, if you're only shooting film, the CA may not be a problem on the 18-200. I've sold all my film eq so I can't really say.
Finally, I've noticed a lot of used 24-120's showing up at under $400. on the used market. When I talk to people they say they are selling to get what they think is going to be their 18-200mm "miracle lens."
Hey, just my humble opinion. Maybe I should submit some photos so you can see the difference in the two lenses.