After writing a somewhat lengthy and abstract entry about JBI yesterday it occurs to me that there's a relatively simple answer to the confusion (see the comments at the end of the entry).
A lot of the difficulty seems due to marketing messages that compare JBI to EJB, when this is not really appropriate.
The reason for that, as I understand it, was to underscore the potential importance and impact of JBI on the industry. This of course remains to be seen.
However JBI and EJB are technically very different and no one should be thinking of one as an alternative for the other.
JBI is entirely focused on an API for integreation vendors. Application developers are unlikely to ever use it.
IONA's implementation, which was demo'd at Java One, for example, allows any JBI compliant integration component to be hosted on Artix. Any vendor of business process management, data transformation, security services, transaction services, etc. can therefore immediately take advantage of Artix's high performance middleware kernel and multi-protocol, multi-format, and multi-language capabilities.
EJBs on the other hand are squarely aimed at application developers and have nothing at all to do with enabling best of breed functionality for customers of integration technology.