I am not sure I understand the benefit of using an event scoped stateful component such as was used in the RegisterAction class of seams-booking. In seam-registration, a stateless RegisterAction is used, and things seem to work fine.
By making it stateful, you can have it keep state between multiple different calls in the same request. This is not true for stateless beans. For example, if the bean is bound to JSF form properties, it must be stateful.