I've had the old 28-70 2.8L for years, and when I "upgraded" to the 24-70 2.8L I was so disappointed in the lack of sharpness, especially at the 24mm end, that I returned it.
Now, I know I could've sent it down to Canon for calibration first.
I'm now planning to get the 24-105 F4L, as a lighter weight replacement for my 28-70 2.8L, which is my current walk around. AND -- upgrade my D60 to a 30D (big upgrade!).
But I, too, am concerned about the roulette game of getting a good "copy" of a high end lens like the L-series products. (I also have a 70-200 2.8L IS -- good, and a 70-300 L IS -- not so good).
Has anyone ever actually spoken to someone at Canon that has discussed the issue?
AND -- are there more "reliable" dealers that tend to not "recycle" a lens that has been returned for lack of sharpness? Do the higher-end dealers perhaps get lenses that test better out of the box?