When I read the rumours a few days ago, I was very 'meh' about the whole idea of a 24-70 f/4 replacing a 24-105 f/4. And I was one of those thinking that it has to be less than the $1150 24-105 or it'd be DOA. (I was also one who thought the 6D must be less than 5D2 or it'd be DOA, but see how well that turned out)
But then I read about the 0.7x MM, and the 4-stop Hybrid IS, and I was definitely thinking "this may well be my kit-zoom if I ever move to FF" (if indeed I ever have a kit-zoom for it, i'm a Prime kinda guy right now).
But then I saw the $1500 price, and was back to 'meh'.
Still, for others it may well be a very good choice, and a very good pairing to a 6D (although I still don't see why you'd buy a 6D over a 5D2). Especially given the 'rebelisation' of the 6D, most people 'moving up' from a rebel / xxxD / xxD (who probably only got their rebel as moving up from a P&S) will obviously need a new lens. And they're also probably the kinds of people who would be more impressed by a 'do-it-all' lens, being able to do decent macros without buying a dedicated macro lens is going to save you $500 or $1000 already. (hell, even I remember my first P&S, I was impressed by the 1cm-macro).
(Also please don't write stuff like "but i'm a rebel user and I want a 6D but i'm not buying this lens because...". You're not. If you're reading this then by definition you're the 1% of gearheads, not the 99% of consumers to whom this is targeted).
As for the price, well yeah. $3500 (probably closer to $3000 in a kit, don't forget a 5D2+24-105 kit was only $600 more than the body-only) is not exactly 'FF For the masses'. But canon's definitely not going back to non-L for FF zooms, probably ever, the 28-135 is probably last of its kind. They'll be more expensive than nikon surely, but they'll really have to make sure the salesmen sell the advantages of Good-Glass(tm) over Better-Sensor.