It's more than just a shared kernel, the development API's allow you to be hardware agnostic while developing as well as infrastructure in place that allows app to app communication and data sharing.
How is this any different than what Linux and other OSes have been doing for years? I don't seem to recall all Linux programs having to be rewritten for each and every architecture (except for some applications that may try to tie in at a lower level)
From the article
Thanks to the sharing of C and C++ libraries, Direct X components and SQLite support, developers can actually write an app once and move it from one platform to another with only a few code tweaks.
Take out the Direct X part there, and doesn't that sound exactly like Linux?
The article says that developers can move their apps around from platform to platform. This isn't like a java JVM in the middle that will interpret your applications compiled code and run it on every architecture. It is just a single OS with a set of standards and libraries that are available on multiple architectures/platforms. All that Microsoft has done is copied the exact model that other OSes like Linux have been following for many years, there is no innovation here. Of course they could extend this to be more like Java, so that programs could be moved from platform to platform without being recompiled, but I don't think that will fit in very well with the big hitter programming languages.
As a whole these are of course good things, but seriously how has it taken them this long to do this? Maybe they were worried about people recreating their libraries so that these apps could be more easily ported to other OSes.
Start menu is back in 8.1 so the cries have not been ignored.
A button that brings up the metro (or whatever it is called this week) interface is not a start menu. I mean a real legacy start menu like Windows 7 (or older if you prefer). I wouldn't recommend that they allow you to remove metro altogether since they want to get their cut from the app creators, but not giving users an option for what they want no matter how hidden it is to enable it feels like a slap in the face. I could see that if no one had told them that users wouldn't like this before they released they maybe wouldn't have included it right away, but people have been complaining about this since the beta so there is simply no excuse left for them. It is just Microsoft's way of telling us that they know what we want better than we do, and they are using their near monopoly on the PC market to force it on us.