Drools is well suited for big projects where business logic and rules must be separated from program code. So they can evolve when business evolves without being tied to code evolution and deployment.
InRule is suitable for when your business rules need to change on a daily basis and you want the flexibility for your commercial team to take the ownership and drive results, without dependency on development teams. It also suited for when you want to quickly prototype new business logic without going through development cycles. It is also suited when you want to have the simplicity in the system so that even managers can jump in and help if needed.
Fusion doesn't support persistence of working memory, which brings some extra high availability risk to our business.
Guvnor still has a lot room to be implemented, it is not so user-friendly for non-technical people, so a lot of business users complain it is hard to master.
Rule execution server doesn't even have JMX implemented, hard to be monitored.
Drools is still lacking support for key Web services standards.
OpenRules provides the non-technical Excel way for a business user to easily modify and manage the rules. Sometimes we found Drools is a little bit overkill for some small and quick projects and we found Roolie is a not bad option as Drools alternative.
The IT department quickly adopted Drools as it is a very good java-based rule engine, which saves a lot of time to meet the project timeline and balanced our business requirements.
Recently we start considering the OpenRules, which may be more business user-friendly.
