I've solved this but it's worth sharing as I couldn't find anything on this.
I had a subclass of UITableView, with a detailTextLabel.text that was not displaying. The detailTextLabel object itself exists as normal, and contains the text, you just can't see it on the screen.
The bug only happens on the iPhone 5 or retina 4 inch simulator. It's fine on the iPod 4 or any other simulator "Hardware". The iOS version used makes no difference.
Answer is below.