> Users of the TAR format usually come from UNIX,
> so using the same command line options should not be so surprising.
Not sure about that: they could be Python users wanting to unpack a tarball sdist.  That said, there is no harm in being compatible, and I like your small list of options.

FTR Lars said that he prefered compat with the zipfile CLI, which is:

Usage:
    zipfile.py -l zipfile.zip        # Show listing of a zipfile
    zipfile.py -t zipfile.zip        # Test if a zipfile is valid
    zipfile.py -e zipfile.zip target # Extract zipfile into target dir
    zipfile.py -c zipfile.zip src ... # Create zipfile from sources