I have no experience with C extensions on any platform. This is all new to me. In another branch I'm experimenting with the techniques used in ruby-atomic. That gem is significantly different than what I did here. I think it is a much better model to follow.

My preference would be to target MRI only. Rubinius built the entire standard library in pure Ruby. So long as we continue to implement pure-Ruby versions of everything then we fully support Rubinius. But I don't know anyone who uses Rubinius in production so I may not have the appropriate perspective.