Nikon's newest lenses are very good, but so are some of the Zeiss lenses. The Zeiss 100mm f/2 is one of the finest SLR lenses ever, but then again that doesn't do you much good if you need a 28mm or 50mm lens (unless you want to stitch everything).
I second the suggestion of getting Lloyd Chambers' Ziess reviews before you purchase, there's a lot of good info there. All of the Zeiss lenses are good, but some are better than others, and some are better suited to certain tasks than others. I have the 100mm f/2 and 35mm f/2. Both are excellent for landscapes. But the Nikon PC-E lenses are also excellent, and offer some pretty compelling advantages of their own. And if you really need the wide FOV, Nikon's 14-24 is well deserving of its reputation (assuming you can live with its limitations - no filter support being a pretty big one IMHO).