[...] while nice to have, are those metadata tags of any great importance? For learning / exif-peeping sure. But for the conversion tool, your favoured C1 doesn't use the camera makers' secret sauce and yet, with some "difficult" images, still does (objectively) better conversion than the makers' own software.
Yes, they don't seem important, but they may be in the future. In addition, some are useful, such as the tah denoting presence or not of the teleconverter (DNG converter ignores this tag).
Sure, if disc space saving is the purpose, it's defeated by embedding the original, but that's not the purpose.
Well, it could be one of the purposes... ORF files are not compressed, so DNG could be a space saver.
Your other point is really about subjective preference for certain raw converters' renditions.
In the case of ACR vs. Oly files, it is almost an objective observation... ;-)
BTW C1 say they will support DNG this year.
Well, they are certainly dragging their feet. So is the developer of Bibble, who says that DNG somehow does not fit well into the conversion method Bibble uses, and would force the software into another paradigm (sorry if I misinterpret here, this is what I recall...)
As for the difference between the same image converted by Raw Developer from an ORF original and from a DNG made from this ORF... actually there is no difference if the DNG conversion used the "Preserve raw image" setting. My first tests used the "Convert to linear image" setting, in which case there is a slight difference in the conversion.