There has been a lot of confusion around the W3C HTML5 Test Suite the last couple of days. It was widely reported that because IE9 seemed to pass most of the tests (many of which are made by Microsoft), it was the most HTML5 compliant browser (which is of course not true).
The HTML5 Test Suite Conformance Results page has now been updated to clarify the situation:
The HTML5 Test Suite Results aims to help implementers write applications that support HTML5. In no way are these conformance tests to be construed as providing certification or branding of HTML5 implementations. The only claim that could be made is that a particular implementation is conformant to a particular version of the HTML5 Test Suite.
It is inappropriate to cite those results as other than work in progress and unstable.
In other words: The results of these tests do not reflect the general HTML5 compliance. They only show which browsers pass those specific tests available at that specific time.
The page also explains that the Test Suite is under development. At the moment, there is a relatively small number of tests, but this will grow over time.