So I have this model and it takes 800 seconds to compile in the front end. Yes, it has some 81 submodels in it, but still... Classic Mx had finished running the script in less time whereas Open is still going after 9hrs (preliminary results only, it is possible that model is mis-specified).
This thread caught my eye: http://www.r-bloggers.com/the-new-r-compiler-package-in-r-2-13-0-some-first-experiments/
Is it worth trying to compile some bits of the OpenMx frontend to improve performance there?