Anyone who cares has heared that IE8 beta 1 has just been released, with quite a bit of documentation.
Mark “Tarquin” Wilton-Jones offers a pretty good overview of the changes. Many are good, and I’m especially happy with the Acid2 support and the decision to make the IE8 rendering mode the default. It is also important to note that there is still “much more” expected in beta 2.