For those interested, there's a video of Ari talking about Terracotta here: http://video.google.com/videoplay?docid=7660457673499305140

Personally, I'm not sure that I'm as enthused. Some reasons:

1) APIs are bad?
Java's concurrency constructs and memory model are poorly understood and error-prone - APIs at least give us a chance to think at a higher level (e.g. process-oriented like CSP). In Terracotta’s case, the missing API complexity is just pushed out to config.

2) Transparency is good?
The level of transparency offered by Terracotta would make it very difficult for application developers to address the usual 'fallacies of distributed computing'. Any field/method access could potentially be remote; any synchronized block could potentially be a distributed transaction (and cause a distributed deadlock). Network failures also seem to be unrecoverable at runtime.