You can also find out about the important changes from:
C-h r m antinews RET
This provides a changelog in the opposite direction, which is entertaining:
For those users who live backwards in time, here is information about
downgrading to Emacs version 23.4. We hope you will enjoy the greater
simplicity that results from the absence of many Emacs 24.1 features.
It can be found online here:
http://www.gnu.org/software/emacs/manual/html_node/emacs/Ant...