We get a lot of support cases where things aren't working correctly due to the fact that Tomcat hasn't automatically recompiled certain JSPs after an upgrade of JIRA.

I'm not 100% sure what the cause for this is (could be customers copying files manually when upgrading therefore changing file timestamps) but we should see if we can clear the work directory automatically when we do an upgrade of JIRA (as part of the upgrade tasks/startup checks)! We should probably make a backup of it.