I'm not sure that changing the default value for "reuse address" justifies breaking backwards compatibility like this. Admittedly, I'm not an expert on networking, so perhaps there's a good reason that I'm unaware of.

As for the queue size, passing 0 to socket.listen() does seem like a more reasonable default than the rather arbitrary value of 5. Again, it's arguable whether it's worth changing this given that it has been like this for a long time, but in this case at least the potential for harm seems negligible.