Exactly what's the deal with the new Ambush/Bstab?

[Phoenix]

I seem to be making a lot of topics recently...

Ok I know that it's getting buffed and that Lethality doesn't affect it anymore (at least Ambush) but how exactly does it work? Is it a damage increase over the board? Or do you need Attack Power+ items for it to really shine? How exactly is the damage calculated?
[right][snapback]73955[/snapback][/right]

We talked about it here. The formula is not quite what russ says.