It make sense if you have an FX body or want to upgrade to and FX camera, other wise it is throwing good money away just to say that you have the newest thing. The MTF chart shown that both Nikkor 35mm DX & FX lens are equivalent to each others on a crop body (the DX version is a smidgen better than the FX), and the DX lens is less than 1/2 the price of the FX lens.
Sigma 35mm f1.4 MTF @ f1.4 shown that it is superior to the Nikkors at f1.8. IMHO, it is highly likely that the Sigma will be a clear superior to the Nikkors when close down to f1.8 to match with Nikkors wide open at f1.8
I concur with your assessment, though how much it impacts the photographer depends on how often they shoot wide open. The catch is that you are comparing lenses that aren't really equivalent marketwise in the first place. The Sigma is an f-stop faster and costs approximately 33% more. Now, if we are saying cost shouldn't be a consideration then we should just all buy the Nikon 35mm f/1.4 for ~$1600 and call it a day. Of course you would then say the Sigma is more value for the money compared to the Nikon f/1.4 and you would be correct, but at f/1.8 the new Nikon is actually priced fairly. As focal lengths get smaller it gets progressively more expensive to make them fast and have good IQ.
In general though, based on the charts the new 35mm should be a solid performer edge to edge once you close down a little bit. Many FX lenses tend to be sharpest around f/8-f/10 so there is nothing new here.
The Sigma appears to be a really good option though for those that want to kick in the extra cash. I guess in the end you get what you pay for. The new 35mm is obviously targeted at prosumer photographers that have moved to FX but aren't looking for pro level gear and is priced accordingly.
AViking: I understand where you are coming from. You have a point. I purchased a D600 myself. Fortunately, my experience has been good overall. As for the first adopter mentality, I not as worried about Nikon's glass as I would be with their bodies. Guess I'll just have to see how it goes.