Yes, I always pay attention during the safety briefing. Yes, I check the lifejacket, count the seats to the exit, read the seatback card.
Extra marks to companies like Virgin who try and make the briefing interesting or amusing, and to crew who liven things up. It makes a big difference: people really don't pay attention to boring things.
Also, what about people who don't know much (if any) English? With modern seatback technology, it would be very possible to have safety briefings in hundreds of languages stored away for recall on demand. I bet if people could rerun the briefing, there'd be a surge of interest following any noticeable turbulence...
R