We found "Issues" to be helpful pre-release. If the issues associated with a Story would prevent it from going live to a production environment, the story would not be included when we branch
for a Release. Sometimes we find issues that would not impact our end users or would not be severe enough for a customer to complain. These issues can be converted to Defects and placed in our backlog for future prioritization while the story would be included
in our release branch. Post-release our defects are related to Feature Groups as opposed to Stories that have already been released.
As for reporting – haven't got that far yet, but I'm sure the Custom Analytics will provide the flexibility to report on issues related to a Story.