The wraps are off the new Zeiss 15mm f/2.8 Distagon ultra wide angle lens. At almost US$3000 and 15mm, it isn't for everyone, but it gives another strong wide angle choice to FX users.
The lens is chipped for exposure automation on Nikon bodies, and weighs in at about 26 ounces (730g). The front element is big (95mm filters), and it comes with a petal-type lens hood. Near focus is about 10" (0.25m). Zeiss claims a low (2%) barrel distortion figure.
Some will want to know what I meant by "15mm...isn't for everyone." Lenses with really wide angle capabilities aren't exactly used for their "wideness." If you're trying to frame a very wide subject, you're probably better taking a pano approach with a longer focal length, because just using a wide angle lens will give you a very flat look and include huge areas that aren't important to you. You get a very flat, distant look if all you use a wide angle for is to frame wider.
Where ultra wide starts to have great use is in altering perpsective: getting really close to foreground subjects and letting the perspective push depth into your subject. To that end, the 10" minimum focus distance is a good thing. With lenses like this new one, you need a really strong near, a solid middle, and a decent far to pull off a great image.