Haven't used EJB3, but by reading a tutorial, EJB3 looks like mostly for manipulating data in database through JPA (of course, it contains other business logic). Just curious, if no database is quired, is it still beneficial to use EJB3 or it just adds complexity to an application? Will POJO be a better choice for implementation?
Big part of EJB benefits is coming from transactions and persistence.
But even without them you may benefit from EJBs. It can give you a proven clustering and balancing model. It can give you the declarative security. It can give you MDBs which are a convenient way to listen to JMS queues/topics and timers.
All above can be done using third-party libraries, such as Spring. EJBs though are highly consistent, while to get, for instance, clustering and security you may need to combine two products, and it's not guaranteed they will work together well and won't need much glue.