I\'m sorry for flaming std::string and std::wstring. They are quite limited and far from being thread safe. Performance wise, they are not that good too. I miss simple features
I found wxString convenient to use and it has many features. Although it is part of a bigger library (wxWidgets) and maybe just too big when you just want to use strings. It also works without GUI components when you just use wxBase which contains the wxString and a 'few' other components.
EDIT: here is a link to the documentation. It accepts the standard functions of std::string and also a few others. I always find the BeforeFirst() and AfterFirst() very convenient when I have to parse some text. And it is really well documented.