Could you please enlight a bit more about first bug that you mentioned? It seems like a very weird behaviour.

Why perl behaves that way? Is it worth reporting via berlbug?

Courage, the Cowardly Dog
PS. While I agree with you about benefits of upgrading to 5.8.0 because of better Unicode support, there are some incompatibilities that makes migration harder. (One of examples is that sockets became textmode by default on Win32).