During the Build 2015 keynote Microsoft’s Alex Kipman mentioned that the enthusiasm from the industry and from consumers for HoloLens has been outstanding:
I have to admit, we have been humbled by the outpouring of enthusiasm spanning from consumers to businesses, and the response we received from developers like yourself, has been remarkable. On behalf of the entire Microsoft team, thank you.
A list of initial development partners was also showcased, and you can see it below. Notably, it includes the popular game engine Unity.
During the presentation, several applications for HoloLens have been shown, introducing the capabilities of Windows Holographics (which allows developers to build Windows 10 apps for HoloLens) and displaying apps placed and resizing naturally in the space and even following the user around in a definitely impressive way.
They ranged from entertainment, to productivity, passing by study and manufacturing. You can see a few examples in the gallery below, and watch a trailer showcasing how the headset is made and how it works.