This is quite an exciting release as Drools has now become a hybrid chaining engine, capable of executing both the reactive forward chaining rules and now prolog style backward chaining rules for derivation queries. We've added a lot more depth and maturity to the business rules authoring with top notch decision tables and rule templates
At the same time jBPM5.1 has also been release, with full details here.
You can see two nice videos on latest GUI stiff in Guvnor video1 (decision tables and rule templates), video2 (Guided Editor)
Mark