&gt; ARC was a bit of a &quot;Hail Mary&quot; and is problematic in its own right<p>I&#x27;m just curious with your experience what you are pointing to as problematic.  Other than potential extra <i>release</i> calls in tight loops, the main downside I saw was it made the use of C structs way less appealing---at the same time, I wouldn&#x27;t want to with manually memory managed C structs in GCD blocks.