I'll admit that i was first in line to crap all over the 6D, it was exactly the same as the 5D2 just in a shinier new case and a few useless trinkets added on, for much the same price as what it replaced. I did, and will continue to, question anyone who buys the 6D as to why they don't buy a 5D2 instead for $500 less (even if you're a rebel user and need to invest in CF cards for the 5D2, they're not $500), unless you have a very valid reason for needing an inbuilt gps and have a total phobia of buying a used 5D2.
This lens, however, is different. I'm still not sure if it's replacing the 24-105L for a start, methinks the 24-105 might continue on for at least as long as it will take for the new lens to come down to the 24-105's current pricing.
But think about if you are one of those who are stepping up from a rebel (or even a 7D, which I eventually will do), you're (probably) not going to have a FF-kit-zoom (i've currently only got the EFs 15-85). When you add in the 0.7x MM figures and the Hybrid IS, this lens looks like a bargain compared to the $2200 24-105+100L Macro combo, plus it's smaller and lighter to boot.
The IQ will probably beat the 24-105, probably not the 100L, and all you're really missing out on is 70-105mm and 0.7-1.0x MM.
Not a big deal for your casual shooter to whom this is aimed (again, if you're reading this forum, then you're not the 'casual shooter to whom this is aimed'. if you're reading this, then by definition you're the 1% of gear-heads, you're not joe consumer).
OK, the price is a bit high for now, and I can't afford it either (neither can i afford a 5D2, even used). But the price should settle at the $1200-or-less mark fairly soon enough.
I predict this lens will be a big seller. Kit this with the 6D and it will account for more reason to buy the 6D than the body (imho).
ps, remember the 70-300L? "Why would I get that? it's variable-aperture and slow, and it's the same price as the 100-400L, i'd rather get the extra reach, whinge whinge etc". What lens sells better, and is generally more acclaimed, out of those two now?