We are running 0.19.2 ES in production which AFAIK uses Netty 3.3.1.Final.
In newer ES releases the Netty has been upgraded to Netty 3.4.1.Final. I
gave Netty release notes (http://netty.io/blog/) a quick look and I can see
bunch of bugfixes between 3.3.1.Final and 3.4.1.Final (are any of them
really serious?). Is there any reason to consider ES upgrade from 0.19.2 to
higher version just because of Netty upgrade? Does anybody run into any
issues because of the Netty 3.3.1.Final?