"Devices & services"
Azure is your servers and the .net + C# tooling story from dev to deploy makes the question of selling Windows servers in a VM world moot. Many of the moves coming out of this Build seem to point to a world where it's going to be cheaper and easier to pay for all the MS services and tooling than to try to cobble it together with other people and platforms.
We're looking at a lowered on-ramp to .net apps that run more smoothly than java+linux+every-support-tool-bit (dev-wise) across devices (and things). It's compelling.
Everything from dev to deployment and ops is getting touched at this conf. This shows where MS's strengths can present differentiation. Their profit source is, and has been, building/selling tools and platforms for others to run businesses. When the thing people hate becomes more like what they aspire to have/be, the tension is palpable.
Google is about the only other player nearly capable. But Google's mission has far less to do with selling shovels vs. harvesting and monetizing.
Apple is just not in this space. If anything, they sure feel like a device-only company in this conversation. WWDC is about the garden. Build is handing out spades, shovels, and, now, dirt.
Xamarin's Evolve, last year, felt a bit like all this does. The are big things happening. If nothing else, at least it feels like change, if not progress for devs and consumers.