Are you using encrypted home directories? If so, the autologin features, and the scripts above + elsewhere, didn't work for me on 14.04 (one of them created a nasty loop which left me unable to login locally; thankfully I could get terminal access through webmin).
Anyway, what did work for me was unencrypting the home directories per the instructions here (modified slightly as I found some bits unclear):
(1) Login to an administrator account.
(2) Open a terminal window and backup your home directory/ies - you will need to do this for all users on the system, as this process removes encryption for everyone. Change 'user' below to the names of your users.
sudo cp -rp /home/user /home/user.backup
(3) Check there are no errors in the copy process; there shouldn't be, but you are about to delete the original, so worth making sure.
(4) Delete your home directory/ies:
rm -rf /home/user
(5) Remove the encryption packages
sudo apt-get remove ecryptfs-utils libecryptfs0
(6) Restore your home directory
sudo mv /home/user.backup /home/user
The original instructions suggested removing any .Private .ecryptfs folders; I didn't have to do this, but you may.
rm -rf ~/.Private rm -rf ~/.ecryptfs
(8) Because I'd already set the user account I wanted to autologin in the system / users panel, when I rebooted it logged straight in.
(9) If you then open the Dash (click the ubuntu symbol in the top left) and search for "startup applications" per the answer above, I had success just calling "kodi".