Adaptive execution plans.
This new feature, by itself will justify many upgrade around the globe.
Most of database operation are repetitions, and as everywhere always have a “bad execution plan” due to lack of precise statistics. And this used to go over and over.
But now the database will gonna behaviour better and better.
I can imagine improvements in more 90% on hardest operation.
Decreasing in CPU demands and memory.
Oracle Logbook 