Here is Phaeden's original post from the old forum, so that those of you who had questions there, will now have answers at our new forum here.
I am one of the core ACE developers. It is Environment [not Element].
ACE, in short, is a complete conversion for ArmA which will bring with it a much more complete and in-depth package to bring ArmA much closer to a simulation (as opposed to a game). That being said, we also understand that the average use is playing ArmA/ACE to enjoy a tactical first person shooter which emphasizes real world vehicles, weapons, and tactics. We know the average ArmA user is not interested in setting the timing on 0.50 Cal M2 machine gun. However, we also understand the value of having a game/simulation which really places the focus on infantry tactics, combined arms, and realistic weapons and vehicle characteristics.
You can expect to see a complex mess of realism and gameplay. It will NOT be for everyone. I don't even think it will be for the majority of ArmA players (based on the response WGL got in OFP). It requires people to think and act tactically and in an effective team. Rambos need not apply.
I will most more specific information in the coming weeks (as I am almost on vacation).