I tried it out and it doesn't work on mine. I read on some
German forum (with what little I could understand) that something
needs to use the HDMI entrance before you can use the dual play
feature.
But I haven't tested the dual play with the PS3 or 360 yet. I
can't be too sure about it not working, but for my TV it's most
certainly not as easy as just turning the TV on and selecting dual
play, since I can't select dual play when using the Wii.