I'm not sure if this is going to be a useful question/thread, as I dont have any concrete examples or snippets to provide.
All I know is that I have been testing my app via simulator (the Retina 4") with no problems. Then when I deploy to a device (via ad-hoc) i see stability issues, like choppiness in animation, general sluggishness, and occasional crashes due to various reasons (mostly it seems to be somewhere with navigating between views).
On previous iPhone device versions things seem to run fine.
The app has a couple of files where the memory is manually managed. All other files are subject to the automatic memory cleanup.
When in doubt...use Instruments! Let it help you isolate where problems are in slow animations. Keep in mind that because there is more real estate on an iPhone 5, it must load more resources, for example, in a TableView.