Rather than continue with unsupported opinion, I'd rather make the specific point that Boost served well as incubator and proving ground for such constructs as shared_ptr and unique_ptr, which have been subsumed into the C++ standard as undeniably huge improvements. As a result, the unfortunate abortion auto_ptr has finally been able to be consigned to a well-deserved resting place in Hell.
Other parts of Boost have been considerably less impressive, and virtually nobody uses them. I struggled at length trying to get Boost::Parameter to work, with zero success. Boost::Format at least works, but ends up cumbersome, and does not approach the usability of {} formatting in Python.