Since the introduction of the D7100 and D5300 and the advent of the Sigma Art and Contemporary lines, there have been numerous reports of interoperability issues that never existed before. These include the consistent issues of the OS remaining on, most reports stating for one minute following activation. There are some claiming either that the switch does nothing and OS remains on even when set to off, with still others claiming that the OS remains on the entire time the camera is on. If true, that would be a serious issue.
The problem with OS remaining on is that it is the outward manifestation of the fact that Sigma and Nikon are not playing well together. We don’t know what other issues exist that we aren’t seeing immediately. For example, many of the folks who have bought these lenses, myself included, have also experienced seemingly random focus problems. For me, the problem is something I can’t force.
I find it interesting that when Sigma was not a true competitor in terms of build quality or (in most cases) image quality, there were no interoperability problems. Sigma generally only made a few lenses where the IQ was on a par with Nikon and those were in areas (the 150/2.8 macro, for instance) where Nikon had holes.
Now that Sigma has shored up their QC, improved the build and is not only directly competing with Nikon but is actually besting them in some spots (the 18-35/1.8 and 50 Art come to mind), suddenly these issues crop up.
To compound matters, there is significant competitive pressure on core products from manufacturers who used to be on the periphery (Sony, Fuji) as well as on core formats from former outliers like micro four thirds. The latter is the least surprising to me given that both the concepts of crop or full frame were based on a limitation (film) that had zero bearing on digital cameras.
Further pressure comes from drastically declining sales, both in dslr lines and p&s products. These declining sales plus the advent of multiple vectors of competition, (and let’s throw in the cost of the tsunami damage to the factories) and there exists a case for saying the days of seamless operation between brands might be coming to a close.
In the past, it might have benefited Nikon to be at least friendly with 3rd party equipment makers but perhaps no longer.