The problem that I have with much of this discussion, is that it is taking place in a world that seems divorced from the realities and limitations of design/price.
Count me as one of those who uses the 24-105 as a basic all-around lens. I was excited to learn about an update and had high hopes for improvements, even though I can't say that I've ever been let down by the current lens.
Initially, I was disappointed with the reviews. Then, I compared this lens to other models. The conclusion, supported by reviews, is that no competitor makes a better lens (neither Sigma's "Art" lens nor Nikon's slightly longer version).
As I've written before, I am one of those who would have paid 50% to 100% more for a significantly improved lens. But, I have concluded that Canon couldn't (nor could anyone else) design a better lens for a reasonable increase in price.
I imagine that designing a lens that goes from wide-angle to telephoto is more complicated than designing one that remains at telephoto or wide-angle. I don't think it has all that much to do with the actual range (although certainly wide range lenses are more challenging) as it does with having to move from wide to tele. 24-70 is obviously easier to design and produce, but can hardly be deemed telephoto.
So, yeah, I have no problem with people expressing some disappointment, but that ought to be tempered with reality. It would be one thing if Sigma, Nikon, Tamron, Tokina, Sony or Fuji made a demonstrably better version of this lens, but the reality is no such version exists.
At the same time, I think it's misleading to simply declare that this is a "kit" lens and therefore expectations should be reduced. It is also an "L" lens and Canon has an unstated rule that "L" versions are the best available version. So, yeah, as customers we should demand and expect the best. But, as customers, we should also recognize that best does not always mean perfect.
As much as I'd like to think there were 'production tweaks' , can't see waht if anything they could do?
