The way he approached the original Lutheran/Catholic talks, the disappointment with the destruction of the JDDF document by Vatican appendix, and then the recent decision to talk to the more conservative synods while acknowledging that would make some things more difficult.
That and if you read some of his books, he cites Lutheran theologians more frequently that any Catholic writer, let alone Pope, has before. He seems to have an appreciation of the concerns of orthodox Lutherans that is different that most. For one thing, he has in the past made an effort to understand what we truly believe, as opposed to the various black legends in most Catholic apologetics.
For one thing, he has in the past made an effort to understand what we truly believe, as opposed to the various black legends in most Catholic apologetics. -- aye and that's a legend for us all -- we think we know what someone else believes and then scold them for that!