They offer, not drop, ACID it seems
"Appealing to a broader church means making slight shifts – and one good example is the decision to offer multi-document ACID transactions, a feature that is generally available from today."
I don't know but, for us, the lack of multi document ACID transaction is exactly the reason why we only use it as logger instead of a wider data storage candidate. It is good to hear they put this into the engine but i just wonder if they implement this there will there be performance penalty? And does it really work as advertised? Honestly i think multi-document ACID transaction is no small undertaking and i only comfortable to use it in wider scope after, maybe, one or two major versions after it is rolled out.