Lens body elements
The pre-production EF 24-70mm f/4L IS USM we handled for this review certainly looked like an attractive little lens - it's decently-built, with fast and silent focusing. The macro mode promises to be a useful addition, although we have some reservations about how easy it might be in practice to light your subject at the very closest distances (but you don't have to use those all the time, of course). However a real question mark hangs over the RRP, which (not unusually for a recent Canon product) looks unrealistically high.
One big question here is why you'd choose the 24-70mm f/4 over the EF 24-105mm f/4L IS USM, which may be 7 years old, but offers a more versatile zoom range at a current street price around £850 / €900. The 24-70mm f/4 is clearly going to have to offer substantially better optics to tempt buyers at anything close to its RRP. This isn't impossible - it's a much newer design, and shorter-range zooms generally offer higher image quality - but we still suspect its street price will need to drop significantly to be competitive.
The other interesting comparison is to Nikon's AF-S Nikkor 24-85mm f/3.5-4.5G ED VR, which is the D600's corresponding kit zoom, and currently retails at a much lower price point (around £410 / €500). This is smaller and lighter than the Canon 24-70mm f/4, and offers a slightly longer telephoto range instead of the Canon's macro capabilities. It's hard not to see this being a more tempting option for enthusiasts looking into buying their first full frame camera, purely in price grounds (and with the option of upgrading to a better lens later).
This all means the Canon EF 24-70mm f/4L IS USM has a lot to live up to - it really does need to be very, very good indeed. As always we're hoping to get our hands on a reviewable sample as soon as possible, to see how it measures up in practice.