Should we consider a C-based implementation like https://github.com/llllllllll/cnamedtuple? It could improve speed even more, but would be harder to maintain and test and harder to keep compatible. My sense is that it's not worth it unless benchmarks show a really dramatic difference.

As for Raymond's list of goals, my PR now preserves _source and verbose=True and the test suite passes. I think the only docs change needed is in the description for _source (https://docs.python.org/3/library/collections.html#collections.somenamedtuple._source), which is no longer "used to create the named tuple class". I'll add that to my PR. I haven't done anything towards the last two goals yet.

Should the change be applied to 3.6? It is fully backwards compatible, but perhaps the change is too disruptive to be included in the 3.6 series at this point.