[bedatadriven]

I think compatibility with GNU R and CRAN is a pretty reasonable goal - even if it's not the focus of this particular Oracle research project.

We've been working hard and now systematically to get Renjin (also R on the JVM) to run CRAN packages: http://packages.renjin.org. Renjin also compiles C and Fortran code to JVM bytecode, though there is still some work to do there as well.

Regarding the hand-tuned matrix math libraries, there's nothing to stop you from using them with Renjin - you can drop in MKL or Atlas as desired, or fall back to pure-Java versions in a pinch.