Should I use printf in my C++ code?

If you ever hope to i18n your program, stay away from iostreams. The problem is that it can be impossible to properly localize your strings if the sentence is composed of multiple fragments as is done with iostream.

Besides the issue of message fragments, you also have an issue of ordering. Consider a report that prints a student's name and their grade point average:

std::cout << name << " has a GPA of " << gpa << std::endl;

When you translate that to another language, the other language's grammar may need you to show the GPA before the name. AFAIK, iostreams has not way to reorder the interpolated values.

If you want the best of both worlds (type safety and being able to i18n), use Boost.Format.

My students, who learn cin and cout first, then learn printf later, overwhelmingly prefer printf (or more usually fprintf). I myself have found the printf model sufficiently readable that I have ported it to other programming languages. So has Olivier Danvy, who has even made it type-safe.

Provided you have a compiler that is capable of type-checking calls to printf, I see no reason not to use fprintf and friends in C++.

Disclaimer: I am a terrible C++ programmer.

I use printf because I hate the ugly <<cout<< syntax.