Read http://forums.cnet.com/7723-7596_102-568853/surround-system-audio-return-channel-system-wiring/?tag=contentBody;threadListing for the short discussion where we cover off why we don't count on it.
If you don't have a newer sound system, you can ignore ARC.
I've bought a TV for the first time in ten years and see that many things have changed.
What's the purpose/reason/meaning behind the (ARC), (DVI) HDMI connections? I'm wondering which one I should hook up through my Blu-Ray and which one I should hook up to my cable box? I also have a third HDMI port that has no extra label.