I don't agree on WEBricks verbose headers being a problem. It should not be used in production anyway and during development getting lots information easily is obviously very useful.
Similarly for binding on 0.0.0.0. If you're running Passenger or Unicorn, this shouldn't be a problem. I don't know about other projects like Thin. But insofar as this is something the core Rails team has control over, we're talking about just WEBrick again, right?
Edit: Sorry if anyone thought this was supposed to be sarcastic; it wasn't.
and now, Thin?