What does PyPy have to offer over CPython, Jython, and IronPython?

Question

From what I have seen and read on blogs, PyPy is a very ambitious project. What are some advantages it will bring to the table over its siblings (CPython, Jython, and IronPython

Answer 1

The most important feature is of course the JIT compiler. In CPython files are compiled to bytecode (.pyc) or optimized bytecode (.pyo) and then interpreted. With PyPy they will be compiled to native code. PyPy also includes Stackless Python patches, including it's impressive features (tasklet serialization, light threads etc.)