As it happens the documentary about BA 09 was on uk TV yesterday and what a frightening experience that was .... and I was only watching it on TV!
I have to say that the it was absolutely the right thing that given the lack of knowledge available that the most cautious approach was taken.
I'm not certain the debate should be "did they do the right thing" but more "could they have lifted the flying bans earlier" and the focus should be (except from the who reimburses who arguments) what can be learned to minimise the disruption without compromising safety in future.
I have seen the BA 09 documentation some days ago and I am really scared, what can happen if you fly through an ash cloud......