Everyone I talk to who knows (knew) about it claims it was the greatest thing since sliced bread. Why did it fail? Or, if it didn't fail, who's using it now?
Zeroconf and other discovery protocols are similarly referred to as the greatest thing since sliced bread; it's just that the flavor keeps changing.
Things have definitely quited down for the idea. Which is strange since you'd think its goals are even more relevant now.
Check out GigaSpaces. It's a quite successful Jini/Javaspaces implementation.
I think Jini has a great model, but it is stuck with Java. Web-services is more appealing because it works with standarized protocols, even though Jini service discovery is more natural.
The jewel in the crown of Jini was it's JavaSpaces service IMO. Sad that Sun seem to have abandoned it. It still exists as Apache River though, however I'm not sure if it's under active development.
My two cents... Jini was/is nice, but I think it tried to be a Java-centric CORBA back in the day when corporations were beginning to be reluctant regarding paying the big bucks for what CORBA brought to the table. WS-* specs began to acquire the "accepted-solution" mind-share in the industry. I think there was a small window where Jini could have grabbed substantial market share, but it never happened. Sun wanted too much money for what Jini brought to the table compared to other alternatives. I would love to hear from folks that disagree! My opinion is that Jini is sound tech, but business-wise has no future in the enterprise. It may find a niche elsewhere, depending on what Oracle decides to do with it.
Jini was an amazing technology. The only reason pushed EJB systems was that it allowed Sun to sell more hardware as EJB ran best on highpowered machines (due to shared state and database access). At the time (1999) Jini allowed much better scalability which ran well on commodity hardware, so it made sense for Sun to not promote Jini. Its a shame as I kept wondering when someone would release an Open Source easy to use Jini server like JBoss did with J2EE. I did however save companies alot of time and money by using the Jini techniques (based on Linda TupleSpaces) and applying them to writing software systems by using Tuple Spaces implemented in other ways.