Descent rate/time/distance
It appears that AF447 hit the water within about 30nm of the last position report. (The June 6 location is about 30' north, the currents from June 1-6 would make the location about 30' south.) The preliminary report would give us that the plane was intact and if not exactly controllable, at least not a lawn dart. We have no way to guess when things went really bad, but we know they started to go bad about the time of the position report.
How fast can you descend from FL350 and still have a mostly intact plane capable of a horizontal orientation by the time you get to the wet stuff? Alternately, assuming the engines shut down for some reason at altitude and wouldn't come back, how slowly can you go down? Keep in mind you want to hit ground within 30-100nm of the initial problem. (Why do I assume the engines shut down? Just because it means you aren't going very far; there is no proof or even indication that they actually did.)