There isn't much new in this release.
There is the new channel switcher and better support for CSS animations, but none of the hoped-for features are yet included. This is in contrast to the nightly build, where one other change has occurred: the URL bar now acts like Internet Explorer 8's, graying out everything but the actual domain name.
Chances are, you won't notice any of the differences, as the channel switcher effectively works in the background (only people who want to change channels regularly will be affected. Personally, I have the Nightly, Aurora, Beta, and Release versions installed separately). One problem that I have with the channel switcher is that there is no way to switch to the nightly builds from the channel switcher, and you can't switch from the Nightly to any other channel. While this may not seem a big deal, it can make a difference when testing (one of these days, I'm going to have time to participate in one of Mozilla's bugdays, but that may be a while) since each confirmed bug in Aurora is supposed to be checked in the Nightly build.