Hi David, sorry about the delay in replying.
Yes, C++ support is complete, but there are memory issues that should not affect you mostly. There's another thread about that... http://sodium.nz/t/current-state-of-memory-issues/204
I actually use C++ on the MSP430 and they don't currently support C++11 which is required for Sodium. FRP is very good for embedded-type applications. I think that FRP on embedded processors is worth spending much more time on.
I did develop a very rough FRP system for the MSP430 that uses lots of templates in order to minimize memory usage. The attempts to save memory/code space are so extreme that it does complicate things, and it's not a true and complete FRP system. If you are interested, I can give you the code for that.