Well what are your thoughts on the example I gave for hash_map? There is always a tradeoff hidden away somewhere. I guess I'd like to see an example of a concrete string type that doesn't incur performance penalties when used in more complex structures. C++11 move semantics / emplace() on containers will fix some of the performance issues with std::string, but support for that everywhere is a ways off. But in C, you'd be left with something like glib's GString which isn't more than API over a struct.