For those who want to delve "inside" the game files, I've created a dumper for ORC files.
http://www.multiupload.com/H4IK07FN8C
To use it, unpack it somewhere and run:
U:\dump\orc_dec.exe "U:\Heroes_VI\Might & Magic Heroes VI - Public Closed Beta\Data.orc"
and so on, up to Data7.orc.
The files will be dumped into the current directory. The source code is included.
I noticed that maps from the campaign don't open in the editor. But this seems to be a limitation of the editor itself, as I rechecked, and the maps are dumped correctly.
It doesn't dump ORC files from the private beta – it has different encryption keys. In principle, it can be fixed, but I'm too lazy.
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I also made a dump for the private beta – http://www.multiupload.com/JV1OA0RPKI
there, not only the keys have changed, but also the file format slightly (minimally).
I didn't see anything interesting.
I'm sure they will change the file format for the release as well. But these are minor things.