Considering GC and concurrency issues, this talk is good for people making language choices on the JVM. In the end, he said he personally thinks STM is not a good way to program concurrency. And, I think immutable data is good for GC.
Or maybe he just learned Clojure people are pedantic and it's more time efficient to agree rather than argue with them.
(the optimistic vs. rollbacks distinction
http://liyang.hu/pub-model.xhtml
http://www.reddit.com/r/programming/comments/daqho/is_transa...
FWIW, why .NET can't have it: