One of the most important uses for HDMI CEC is in fact to wake your TV up from 'Standby'. Why? Well almost all TV's when placed into 'Standby' mode unfortunately also power down their network interface chip too, which means you can't use IP control to wake the TV up. However HDMI CEC is always waiting for commands, and is never powered down when your TV is in 'Standby' mode - unless you set your TV to power it off in 'Standby' that is.
This means therefore placing an HDMI CEC controller behind your TV's - even your brand new SmartTV's, is about the only solution to powering them up from 'Standby' under control of your system. In fact we have many installations that simply use our Dianemo Raspbmc-CEC software for Rpi even with a brand new SmartTV, which has in own built uPnP media playback capability, to just to wake the TV up from 'Standby'. Even systems that have traditional Media Managers driving their TV's can use our Dianemo Raspbmc-CEC software on Rpi to send on/off commands to their TV's.
Whether your planning to use your Rpi with Raspbmc-CEC firmware as a upnp media player and UI (ie a replacement for a Media Director) + CEC controller or purely as a CEC controller for your TV, you can use your Orbiters UI to send control commands to the Rpi to browse, select & stream media and also to power on/off your TV.
How many TV's support HDMI CEC control? In our experience if your TV has an HDMI port and was manufactured in the last 6 years it will almost certainly support CEC and specifically at least On/Off. So you may well have an older TV that has no RS232 or IP control capability but has an HDMI port - this almost certainly means HDMI CEC control is possible.
Find out more about Dianemo CEC Control for Rpi here; http://www.ellipticalcurve.com/dianemo-products-services/
and info about Dianemo Licensing offers here; http://forum.linuxmce.org/index.php?topic=8880.msg100221#msg100221
Whether you have a LinuxMCE or a Dianemo Installation if you have any comments or questions about CEC control, or anything related to it, please post them here in this thread. You can also email or PM me - see the footer below for details.
All the best