A "fun" exercise in C++ is to take a line of code that makes extensive use of advanced features, like templates, smart pointers, etc. and step through a -O0 compile with gdb. I was shocked, in some cases, about how many different functions were called for what looks like a simple expression.

This can lead to some interesting errors. For example, writing

void foo(const std::string s)

by mistake, instead of

void foo(const std::string &s)

won't result in a compiler error, but will result in an unusually large, and unexpected overhead in calling foo.

On the other hand, STL is great (less the error messages). I sorely miss it when programming in C.