title: Why wasn't PyPy included in standard Python?
body: <p>I was looking at <a href="http://pypy.org/">PyPy</a> and I was just wondering why it hasn't been adopted into the mainline Python distributions. Wouldn't things like JIT compilation and lower memory footprint greatly improve the speeds of all Python code?</p>
  
  <p>In short, what are the main drawbacks of PyPy that cause it to remain a separate project?</p>