I think that a clear difference is that Property Tree is intended to support I/O of configuration settings, and of other kinds of human-readable data files. I could well envision an application
The same woth PO. PO doesn't deal with config file generation but that (as I mention in my review) is completely unnessesary anyway. Why and how frequently would I want to generate my config files programmatically?
that uses both libs: program_options to handle command-line parameters, and ptree as a storage format for its data files.
program_options has is't own facility for that.
I agree with many of your other points. In particular ptree could be made leaner, and the double-indexing may well be overkill (I haven't looked at the implementation itself). But the needs the library seeks to address are very real.
Could be. But PO already doing everything this library does. Any specific examples of what is missing (other than some extra parsers for xml and registry)? Gennadiy