The main thing that sucks about shared_ptr's is that they break C++'s limited support for covariance. For example
class A { ... };
class B : public A { ... };
// Totally works
class AFactory {
public:
virtual A* makeOne();
}
class BFactory : public AFactory {
public:
virtual B* makeOne();
}
// totally doesn't
class SharedAFactory {
public:
virtual boost::shared_ptr<A> makeOne();
};
class SharedBFactory {
public:
virtual boost::shared_ptr<B> makeOne();
};