Update!: The latest version of Revolution R, which added support for RHEL 6, appears to work (it appears to at least install, run, and perform basic tasks). See this post for more details. I’ve come to enjoy using R. I had dabbled with it in the past, but found it painfully opaque, and the Effort:Reward 






Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).