Biggest thing for me as a FFer is that I like to know the take-off to touch-down length - how long we're going to be in the air (approximately). Just gives me a little idea of when we'll be touching down to help me plan for my arrival (several times, I've been able to clearly gauge if I can go to the nicer lounge one concourse over, or knowing that since I had a hike for a connection to go straight to the next gate and not even think about the lounge).

As for announcements, one before take-off is more than sufficient for me - flight lengths, any expected weather troubles/turbulence, etc. And one in the descent saying we're 20 minutes out/100 miles out (I'm a fan of getting both of these numbers, again to calculate arrival time...)