Configurable email alert settings
It would be excellent if users could configure email alert preferences to only be notified when comments are added to issues rather than to any change made to an issue. Some users don't care about status changes and administrative details.
It would also be great if users could elect to receive email digests of activity on issues at user configurable times (e.g. "Email me a summary of changes on my issues at 5am daily") as an alternative to receiving individual alerts for each change. This could significantly reduce email overload for users who are just tuned in for informational purposes and are not actively engaged in activity on an issue.