Again a year later....I can confirm fail-over is key to Jade, to mention a few of the mechanisms: backup platforms, the concept of virtual replicated agents, stateless mediator containers (deal with disconnection and ip change), persistent message delivery. Wade adds more to fault tolerance: http://jade.tilab.com/wade/doc/WADE-User-Guide.pdf.
Jade does not mostly target GUI development.
Another strong feature in Jade I would like to mention is that agents do not require open ports for bi-directional communication over the network, only the platform and backups need open ports.
Furthermore STM (finite state machine) is an important part in Jade, FIPA conversation models are implemented using STM. Jade agents do not so much send and receive messages but execute conversations in workflows.
Clustering is not available in Jade, though Wade provides configurable agent pools where a pool of distributed agents take care of a certain task.
As to Elastic scaling and Jade some research has been done, I don't know the status of that. Perhaps it is better to address elastic scaling at the jvm level.
A theme that needs attention in both Jade and Akka is security (identity, authentication, authorization) in a distributed message based solution.
Concluding this: Jade is far more powerful and feature rich then a first glance reveals. Jade needs modernization.
It would be interesting to investigate how Akka and Jade can mutually benefit, the AkkaAgent.