Earlier quoted context omitted.
Then I suppose you don't care about: * Performance * Support for localization (as the format string and positions of values to format differ between languages). * Code reuse & dogfooding - the data structures used in iostreams are not used elsewhere, and vice-versa * C and OS interoperability - as you can't wrap a stream around a FILE* / file descritor * bunch of other stuff... iostreams work, but are rather crappy.
I care about performance, when it actually matters to acceptance testing. The less C the merrier. If you care about correct use of localisation, standard C and C++ libraries aren't really what you're looking for, or even C and C++ to start with.
The only reason why iostreams are slow is because of its incompatible buffering scheme, and the fact that C and C++ need to stay in sync when linked together. And that brand of slow is still faster than other languages, except sometimes those that delegate i/o to pure C implementations.