no one wants to use a public format for model loading (except maybe sid...) as that will always be a lot slower. Those are using our own format wich we can load several times faster than it would be possible with any of the commonly used ones. I am quite sure that unity uses a custom format, same with gamestudio, ogre, cryengine and most other engines out there. Because it really is worth it.
So far I converted all models per hand using a blender exporter I wrote but in the future we will provide some other ways to convert all major formats to our custom one.