Do Not expect the XBMC plugin to work correctly or function 100 percent. A lot more needs to be done before all the features will operate. People will also need to learn how the features work.
A mouse and maybe a keyboard would be good additions to add to your receiver. I have a wireless mouse and wireless keyboard. You may also use the remote which takes longer to do simple tasks. To exit out of XBMC, press the Power button on the remote. Doing this will cause the shutdown menu for XBMC to appear.
Remember, XBMC is a work in progress. Using it right now more or less puts you in a beta testing situation. XBMC should be available in all popular and well supported images in the near future. This will take place as the bugs and issues are worked out and the plugin becomes more usable.