I don't know about everyone else, but I really do pay attention to all safety briefings to the point that even if I'm engaged in light conversation with someone, I will usually stop them and tell them I want to listen to the briefing.
Even if I'm extremely tired and all I really want to do is sleep, I will try to stay awake for the safety briefing if nothing else.
I still locate my two nearest emergency exits (and how to open them if I have to). I still note where the oxygen masks will pop down from and visualise how I will react when they do. I still test whether I can reach the seat in front of me and then mentally note how to assume the correct brace position. I still feel where my life jacket is.
Too extreme? I think not.
My first flight on a Fairchild Metroliner 23 in August 2008 was a novelty. Here the phrase "subtly, every aircraft is different" is way off the mark - the differences in safety procedures from any aircraft I had flown before - jet or turboprop - to the Metroliner was anything but subtle.
Seriously, FAs do not demonstrate the safety procedures just because the law says so, or for kicks and shiggles. I think we have to respect that.
I appreciate that the safety demo is an extremely important part of the flight, that's for sure. And if i'm not flying on a QF 747/737/330/717, a JQ 320/330, An AA 737/MD80, an AS 737, i'll pay full attention. I know the demo run-throughs by heart for all these airlines/aircraft types. In the case of AA and AS i'll pay attention if it's been a long time since i've been on one of their aircraft.
The more I fly the more I become aware of how important safety is, so i'm well prepared in the event of an unlikely emergency.