This document lists implementation feedback about XML 1.0 implementations known by the XML Core Working Group at this time.
There are XML 1.0 Fifth Edition specific tests--along with other XML tests--available via the XML Test Suite page.
There is not yet any feedback available on Fifth Edition implementations.
A not-yet-released verion of RXP 1.5 passes all the tests for errata to the 4th edition.
Intel has developed an internal implementation of the XML 1.0 Fifth Edition PER that passes the 20080205 test suite.