You're overselling it. While you can call C code, the interface is often not very Nimrod-y and it's not automatic, you have to declare prototypes, and there are absolutely holes in the stdlib - the lack of any arbitrary precision/bignums library for instance.
> Library situation is a little iffy. Libraries are hardly iffy. Any C code be called, and most c++ code can be called very, very easily and with little boilerplate. The standard library has a huge pure section, and for almost everything else it has dozens of bindings to C libs. And there are plenty of existing libraries in the babel library manager, such as SFML.