It's interesting to see how certain DVD specs/features are interchangeably marketed on the back of DVDs. For instance, would you consider THX certification an extra or technical spec? Or how about close captions? I personally think CCs should always be a technical spec. The THX one, I'm not so certain about. The cert doesn't carry the weight it did with LDs, but newer titles with it do offer the Optimode feature, which is technical in nature. I'm sure there are others that I'm missing. What are your thoughts? P.S. Sorry if the topic header mislead you into thinking that we're talking about mass, weight, luster, or any other things normally associated as "scientific" properties.