Err, why? It's fairly easy, and you get so much for free: portability, compiler optimizations, easy use of C libraries, easy interfacing with other languages...

why?

One good argument I can think of would be compile time. C compiles slowly compared to almost every other language not C++. And of course you get the C compile time on top of the compile to C time, so I expect the Nimrod compile chain to be quite slow.

Doesn't mean that I am generally opposed to compiling to C, it's often a good trade-off.

A good solution to this is to go with a language like C-- (if you are too scared of LLVM).