Power on/off is nowadays a bad move for most electronics. They are getting closer and closer to computers (when they are not actual computers; that includes all HD players) and computers don't appreciate having their power yanked out.
This is not true any more unless you're talking about servers. In the past, hard drives were an immature technology and the more times they were spun down and up, the shorter their lifespans would be. The electronics in modern computers and modern home theater electronics is more than robust enough to withstand regular power cycling.
Don't let this myth prevent you from saving electricity.
