The Jira integration is really good (tested it briefly), but we've decided that Jira is too complex for our Development Projects at this time.
But the Trello tool is perfect for us. I love the ability to add to Jira by just clicking on the Jira Button while viewing a Topic. This is the functionality I desire for a Trello integration.
The Zapier based integration is not nearly as practical as the Jira integration because it is only triggerable on new Topics (right?). This is both too much (we don't want everything in Trello) and too late (we want to be able to selectively export and link Topics to Trello from time to Time).