A post on the IEBlog on the upcoming IE7.
# Support the alpha channel in PNG images. We’ve actually had this on our radar for a long time, and have had it supported in the code for a while now. We have certainly heard the clear feedback from the web design community that per-pixel alpha is a really important feature.
# Address CSS consistency problems. Our first and most important goal with our Cascading Style Sheet support is to remove the major inconsistencies so that web developers have a consistent set of functionality on which they can rely. For example, we have already checked in the fixes to the peekaboo and guillotine bugs documented at positioniseverything.net so use of floated elements become more consistent.