We certainly can't know for certain. But we've had a significant, measurable reduction in CPU cost due to "hidden" memory allocations from things like passing a char* into a function that takes a std::string and stuff like that. (I may be being mildly inaccurate, as I wasn't the guy doing the perf captures etc. I just talked to him about it).
I'm particularly impressed by AStackString, which is a subclass that has initial memory allocated on the stack, but automatically converts to dynamic allocation if you exceed that space. So we get quick stack allocation by default, but it will safely handle when it needs to expand.
Most of the quality of life stuff is around having in-built support for printf style formatting, string searching (including case-insensitive).
I'm particularly impressed by AStackString, which is a subclass that has initial memory allocated on the stack, but automatically converts to dynamic allocation if you exceed that space. So we get quick stack allocation by default, but it will safely handle when it needs to expand.
Most of the quality of life stuff is around having in-built support for printf style formatting, string searching (including case-insensitive).