There are things which are slower, but since it is a higher level language it may be easier to try multiple algorithms one of which may be significantly faster. It also has many useful features included, which can be optimized in ways that aren't recommended for user code. (writing the algorithm in NQP) There is also a code specilizer (spesh) and a JIT.
Basically for many things it can be fast enough. Also if you profile your code and find something that is egregiously slow you should report it. Many times such things get optimized quickly.