This is great. Before I read all the replies I wanted to say that upgrading Ace was on our list anyway.
But it seems that Laurent wants to get rid of it. I actually hoped that it would be here to stay, but if Code Mirror has the same functionality as Ace, I don’t care.
e.g. I really like the fact that I can move lines up and down with Opt+Up and Opt+Down.
However, I have the feeling that Code Mirror is more visual than text. And I really like just simple text in the editor. But I could be wrong.