Even though the announcement makes the point that synthetic benchmarks are "at best not very useful" because they aren't representative of real-world usage, Microsoft was happy to show off just how fast IE9 is. The differences between most of the browsers amount to tiny fractions of a second, but the latest preview of Internet Explorer still manages to edge to the front of the pack in the SunSpider benchmark.
Sayre saw this as an anomaly and implied that Microsoft was trying to fix the numbers by specifically tuning the browser for this particular benchmark. He even submitted it as a bug to the developers.
Sayre wasn't satisfied by this explanation, though, and argued that, while this approach was valid, IE9's implementation was selective, inaccurate and only removed inexpensive operations. It is, however, triggered by the specific operations found in SunSpider, making it impossible to call what the Internet Explorer devs had done a "serious general purpose optimization".
The Mozilla developer admitted that he "could be missing something", especially since the IE9 releases are still developer previews, but appears to be standing by his assertions for the time being.