“Here’s the way I look at it, and as you said, the ship has somewhat sailed: I am totally convinced that ARC is the right way to go upfront.”
The garbage collector pitch is that you never think about memory. Lattner’s answer is to ask whether that is true. It isn’t. When the collector does something you don’t want, you are thinking about memory again with no tools to fix it. ARC makes you pay the cost up front, where you can see it.