New OpenEXR support in Blender

Ok, new OpenEXR support in Blender has been implemented. I’d like to have more infos about this format and please, explain me for what it could be useful.
I tried saving an image in EXR and displaying it with exrdisplay give me a turned over image :o
I read on the official OpenEXR site this is an HDRI format. But I’m used to see HDRI images (and use them in yafray) as angular maps mapped on a sphere.

So, what is it?
Thank you.