This document lists implementation feedback about XML 1.1 implementations known by the XML Core Working Group at this time.
There is an XML 1.1 specific test suite--along with other XML tests--available via the XML Test Suite page.
The latest test version of RXP (1.4.0pre9) supports XML 1.1 and passes all the tests in the XML 1.1 test suite. It incorporates code from Martin Duerst to optionally check for Unicode character normalization.
See the RXP page.
Xerces-C++ version 2.3.0 includes "a full experimental implementation of XML 1.1, W3C Candidate Recommendation of October 15, 2002 (Note: section 2.13 [character] Normalization Checking has not been implemented)."
See the list of features.
Xerces2 Java version 2.4.0 "is now able to parse documents written according to the XML 1.1 Candidate Recommendation, except that it does not yet provide an option to enable [character] normalization checking as described in section 2.13 of this specification."
See the release page.
"The Corel XMetaL platform supports XML 1.1". See the FAQ.
However, it does not support character normalization checking.