I have noticed my percentage goes down fairly fast sometimes, but I have never ran it down to the point of the computer "dying."
Yesterday I was running on one brightness notch, and it estimated around 7 hours.
Right now, i'm doing the same thing, and its estimating around 11 hours.
Have you literally ran down the battery to the point of it shutting the computer down, or is the percentage just displaying faster rate than actual depletion.
In fact, sometimes the thing will have a low estimate of around 4-5 hours after about an hour of use, but then 30 minutes later you check again and it estimates 9.
I dunno. Mine has stayed on long enough for me to do what I need to do during the day so far, so it doesn't really matter to me, but it just seems like the estimates/percentages are a little out of whack sometimes.
I might be completely wrong, but you know. hah.
EDIT: I just turned up the brightness to 50% and its still depleting the same speed! (slow, around 10hrs as advertised.)
who knows? heh.