String::operator<<(String& string1, size_t number)

can we get this added?
i find myself doing this in DBG all the time:

DBG( "checking " + String(vector.size()) + " items" ); 

it would be nice to have either a operator<< or operator+= for size_t

Yeah, this is probably something we could do now. In the past we always had to avoid it due to old Visual Studio versions having overload ambiguities involving size_t, but now those have gone away we can start adding overloads.