You just used the phrase "catch up" (twice!) to describe other browsers that are far ahead of IE in pretty much every objectively measurable respect.
Clearly publishing a comparison of a "platform preview" (i.e. not even a nightly, it's just the core rendering engine) against the stable, released versions of other browsers is an effective psychological manipulation when even someone who is pointing out that very fact can jump to the conclusion that all these other browsers haven't progressed in the meantime.
Er, the test is an "objectively measurable respect" in which the IE9 Preview is ahead.
Having said that, sorry about the poor wording. And I agree that the released version of IE trails the released version of all other browsers. This has been consistent over several major release cycles. Still, I think MS should be encouraged when they're heading in the right direction.
Clearly publishing a comparison of a "platform preview" (i.e. not even a nightly, it's just the core rendering engine) against the stable, released versions of other browsers is an effective psychological manipulation when even someone who is pointing out that very fact can jump to the conclusion that all these other browsers haven't progressed in the meantime.