The STL does one thing very well: it's very predictable performance-wise while being reasonably useable.
When you use it, you know perfectly what the performance is going to be.
It also offers some occasionally-useful features (std::weak_ptr for instance). c++11's move constructors and rvalue references are very good for squeezing out the last bit of performance where possible and for ensuring exception safety to certain operations; although it's mostly useful for very low-level, entrenched libraries such as the STL. Lambdas are syntactic sugar, but a well flavored one.
c++ is now a very different beast than it was in the 90s. If used properly, it can be very effective (performance-wise) in complex projects. But it can also give programmers tons of rope to hang themselves with.