What do you like best?
The highly active community maintaining and support the product, as well as the price! The community around OSSEC is highly active on forums and other sites and more than willing to help with any configuration issues that come up. Also, OSSEC maintains regular to fix bugs and improve features. Since there is a very high cost associated with other commercial products in the same space, many other companies seem to have also decided to invest resources in this excellent open source product
What do you dislike?
The high configuration overhead of the system. Be ready to have engineers spend time to debug and validate the configurations and systems that are a part the system. As with any open source system, sometimes the documentation and other internet research tend to lead down the wrong path. Having quality engineers be able to handle, maintain, test the configs are a ciritical part of making OSSEC work in production.
Recommendations to others considering the product
Make sure that you can maintain be configuration overhead of the product
What business problems are you solving with the product? What benefits have you realized?
Compliance needs for endpoint security without the ever-scaling costs of per box pricing. Also, by free ourselves from our previous vendor, we've been able to use the same budget to invest more in log rentention and other critical aspects of the business.