Update: Emacs22 is now available via apt. Before trying this try sudo apt-get install emacs22. You will still need to edit your .emacs file as instructed in the last paragraph to handle Java annotations.

Emacs 22 is now released. I have installed on my Ubuntu Feisty Fawn system. The package is not yet available on the apt repositories, so this required building from source. Here are the steps I followed:

Install prerequisites as follows:
sudo apt-get install g++
sudo apt-get install libgtk2.0-dev

Download the source from http://ftp.gnu.org/pub/gnu/emacs/emacs-22.1.tar.gz.

After unpacking, run:
./configure --with-gtk --enable-font-backend --with-xft --with-freetype
make
sudo make install

Voila! The executable is now installed at: /usr/local/bin/emacs-22.1

The java-mode still does not handle annotations correctly. Getting around this requires adding the following to the ~/.emacs file. It simply treats annotations as comments:

(add-hook
 'java-mode-hook
 '(lambda () "Treat Java 1.5 @-style annotations as comments."
    (setq c-comment-start-regexp "(@|/(/|[*][*]?))")
    (modify-syntax-entry ?@ "< b" java-mode-syntax-table)))