Reference documentation is available here here (generated with staticdocs). A tutorial introduction to making compiled systems is available on the wiki. General tutorial documentation is not available yet.
As an example of what I'm aiming for, here is a simple harmonic oscillator, implemented as a function. The embedded R code at the bottom will run when passed through
Similarly, here is the same system implemented as a small class. The book-keeping here is slightly greater, but allows for arbitrary calculations after parameters are set (e.g., precomputing values that would be used at all times).
The package is not yet stable, but most features are now in place aside from better deSolve support and low level stepper features.