As reported in my previous posting, I've been working on the new XML Schema Test suite. Achieved a significant milestone today: all the tests in the Microsoft part of the test suite are now "done". That's around 14600 tests. Of these I have queried the results of 858 tests (you can find the bug reports in the W3C public bugzilla). Most of these are illegal regular expressions in supposedly valid schemas. Of the remainder, Saxon fails on 22 tests for known reasons, and passes on the remainder.
The failures are essentially for three reasons: (a) hitting resource limits on large minOccurs/maxOccurs values; (b) Saxon has a better algorithm for testing type subsumption than the one in the spec (it's essentially anticipating the XML Schema 1.1 spec here), and (c) there are three tests in which a user-defined type is derived directly from xs:anySimpleType, and although the spec appears to allow this, it's not at all clear what it's supposed to mean, so Saxon disallows it.
I had to fix quite a large number of Saxon bugs to get to this point, but they were almost all very obscure corner cases.
Next step is to tackle the Sun and NIST tests. On past experience these will be easier.