For an interchange format it's not really that important -- games don't use Collada/FBX/ogex files directly, so they don't have to be optimized for loading. You should always convert from your interchange formats to a binary format that's optimal for your specific engine.
Interesting. Can you save the file as binary? That would be an important feature.
These are just some of the reasons we created the Open Game Engine Exchange format (OpenGEX):
It might be interesting for OpenGEX to additionally define a game-ready binary format that's useful for 90% of devs though
When I started using Collada I was worried about simple 1MB models being stored as 60MB of text/xml... But it seems to work fine as all the decent repository systems compress text files before storage/sync anyway.
It slows down the art pipeline. At critical parts of the project your going to be exporting huge scene into your world editor, maybe 100's of times a day.