if you are talking of IQ then yes 2 lens of less focal length is better then i "do it all" lens. Then thinking in ease of use were u dont have to change lens the a "do it all" is were it is at, but lens such as the Nikon 18-200 VR and the 18-250 makes me question why do people buy SLR if they want a lens they never have, and never will change lens. To me that sounds like someone who a P&S/Super Zoom would be good for.
I strongly disagree with your assesment about doing it all. The L lens is in a league of its own compared to the kit lenses. For another, some people can't or don't want to buy another lens, but they like the versatility the DSLR can do as far as adjustment and picture quality with the entire system. Some people just like having a big flashy camera.
Kit lenses are just that. They generally are lenses that are of mediocre quality that can offer people the versatility of up close and descent zoom @ a desent price. It gets their feet wet and hell maybe they'll never need anything better. That L lens is vastly supior to any AF-S or anything short of another L lens. Am I saying that all non-L lenses are junk, no, of course not. Just saying that the majority of the time, an L lens is a long term investment.
I bought a Sigma 80mm zoom "macro" lens. It was a long time ago and I learned a lot with it. I had a Rebel G at the time. I still have it and still use it. For $80 though, the manual focus ring catches but it still performs ok.
I understand that Tamron and Tokina, maybe even Sigma can make a lens the is close in quality, but in the end, a Canon L lens costs as much as it does for a reason. You are getting great optics, killer build quality, and smooth quiet zoom. I've got the nifty fifty. Good example of a cheap, great lens. Its cheaply built to. But for $80 if I drop this, I won't shed a tear....
I would like to know where the OP got the lens for under $500 brand new. Considering they are going used for $430 on average on
ebay.
-JD-