I decided to go with T-Mobile to trade in my 16GB Space Grey iPhone 5S from AT&T. They are giving me $352 (locked in since I won't receive my new iPhone for 1-8 weeks), as well as paying my ETF to leave AT&T, so about another $220-$240.
I imagine the always-listening state uses more power, but I also assume they intend its use for places where you probably have it charging but not necessary able or willing to hold down the Home Button and look at the screen. Examples, might be while driving, "Hey Siri… Get me directions to the nearest gas station," or while in bed with your eyes closed, "Hey Siri… What time is it?"
Not quite a fair comparison since we're talking about CDMA v GSM. We can say that CDMA is king of shitty and archaic (even though CDMA voice on Verizon still much better than voice on AT&T's '3G'/'4G') but we really can't say Verizon was dragging their feet. On top of that, SV&D has been possible on Verizon's network for at least a couple years now providing you had enough antennas to make it work. The previous iPhones didn't.