<p>One of my API calls can result in updates to a large number of objects (Django models). I'm running into performance issues with this since I'm updating each item individually, saving, and moving on to the next:</p>

<pre><code>for item in Something.objects.filter(x='y'):
    item.a="something"
    item.save()
</code></pre>

<p>Sometimes my filter criterion looks like "where x in ('a','b','c',...)".</p>

<p>It seems the <a href="http://code.djangoproject.com/ticket/661" rel="nofollow noreferrer">official answer to this is "won't fix"</a>. I'm wondering what strategies people are using to improve performance in these scenarios.</p>

You need to use transactions or create the sql statement by hand. You could also try using SQLAlchemy which supports a few great ORM features like Unit of Work (or application transaction).
Django transactions:
http://docs.djangoproject.com/en/dev/topics/db/transactions/?from=olddocs
SQLAlchemy:
http://www.sqlalchemy.org/