Watching a DVD on my TV using 10.1.3 is now as simple as it could be on my Rev. A PowerBook G4 (400).
Whereas before I had to boot the PB in "clamshell" mode with the TV connected in order to see the DVD, now I merely need to plug in the connection (I'm using the S-Video port) and start the DVD application. No reboot or sleep required!
The trick is the new "Detect Displays" button in the Displays preferences pane. After connecting the TV, click on that button and the desktop will be mirrored to the TV. Even cooler (though I'm not sure of the danger factor) is the fact that disconnecting the TV with PB on and then clicking the "Detect..." button reverts everything back to normal. Again, no reboot or sleep required.
Since I have the Rev. A model, I cannot mirror the DVD on both the TV and the computer screen. And, with the TV connected the DVD is automatically shown on the TV. Moreover, I can't see the DVD (ie, there's sound but no picture) if I'm in the OS X equivalent of extended desktop mode.
All in all though, the simplicity of watching a DVD on my TV couldn't be any...er...simpler. Very exciting.

