title: Are there any reasons not to use an OrderedDict?
body: <p>I'm referring to the <a href="http://docs.python.org/2/library/collections.html#collections.OrderedDict" rel="noreferrer">OrderedDict</a> from the <code>collections</code> module, which is an ordered dictionary.</p>
  
  <p>If it has the added functionality of being orderable, which I realize may often not be necessary but even so, are there any downsides? Is it slower? Is it missing any functionality? I didn't see any missing methods.</p>
  
  <p>In short, why <em>shouldn't</em> I always use this instead of a normal dictionary?</p>