Notably better AI, if you know how the AI in ArmA was.
They cover eachother, and are using bounding overwatch tactics, position themselves in a way that covers the best angles etc.
It's ofcourse a bit rough but for an open-ended game like this it's mighty impressive imho, even more so if you consider the AI isnt just infantry, but flies planes, helicopters, drives tanks, boats etc too, and on top of that even is capable of some RTS stuff as commander AI.
I like the new radio sounds too.
Several sentences are still obviously chopped pieces, but there are a lot of sentences that sound quite natural now too.
Overall i like it.