Heya,
0.19.0.RC2 released fixing a major bug in byte buffers handling in the networking layer introduced due to an optimization done in 0.19.0.RC1. It is fixed with the optimization still in place.
It also comes with 2 nice features, blog post here: http://www.elasticsearch.org/blog/2012/02/08/0.19.0.RC2-released.html.
-shay.banon