From BOAC, whose opinions I respect highly...
Indeed, singpilot's post is spot on, but do not forget we do not know if any other 330s had the same series of 'failures' that night on that route, nor does the fact that 1 Qantas 330 suffered a serious pitch excursion while others flew happily along mean there is not an underlying technical issue. Unfortunately the chances of the CVR being of use are practically nil, so we have to go on what is 'known'. You cannot just fold your arms and say "crew issue, full stop"
You have to understand how difficult it is for one crewmember to suspect another ESPECIALLY when the suspect crew is not here to defend themselves. I abhor the thought that someone would do that to me.
The CVR is my friend. Automation, properly understood and with training and diligence attached is an even better friend. There are previous instances of 'incidents' that might fit the AF447 scenario, and almost no imagination is required to make these incidents 'fit'. But I still believe what we see in the ACARS messages is a result of the upset at cruise. This aircraft behaved as ANY aircraft would on a night like that presented with the same scenario. Is why I answered the post about 're-creating' AF447.
So here we are, long time, no concrete answers. A lot of speculation (including mine), and most of the speculation centers on technical issues ad nauseum.
What I tried to present was where we stand at the moment. We won't know much from the DFDR beyond what we already have from the ACARS. Both probably lost power at the same time. What we WILL learn is from the CVR... what was going on in the cockpit up to and including the departure from cruise flight.
If it is not found, we will be where we are now. Toulouse may find something in the debris inspection that the Braziliians missed, but I doubt it, even with motivational differences.
Every night since this crash, I have pictured the route and it's special challenges, and can empathise with the relatives of the pax AND crew.
Lest we forget, there but for the grace......