I recently reinstalled my HTPC using Fedora 19 and, of course, installed XBMC on it.
Here’s how to get Fedora to boot to XBMC without login.
First, configure your desktop manager to auto-login. In my case that is LXDM and it’s configured by editing /etc/lxdm/lxdm.conf and adding/changing the line containing autologin=USER with USER being the username of the local user you want to run XBMC as.
Next, change the desktop manager for your user to XBMC. If you install XBMC using the Yum package you should have gotten /usr/share/xsessions/XBMC.desktop so it’s enough to create a file called .dmrc in the user’s home folder.
(End by pressing CTRL-D)
Finally, to prevent XBMC from using CPU when on the home screen, disable the RSS feed by editing the settings for the default skin. Edit ~/.xbmc/userdata/guisettings.xml and change enablerssfeeds to false.
Reboot to confirm XBMC does indeed start automatically after boot and run top remotely to check the CPU usage.