Persuading the DRUPAL-5 and DRUPAL-6 branch maintainers to change their policy of not fixing bugs in their branch until they've been fixed in the development branch is what's important.
This is an accurate summary of what I barely managed to say in a couple hundred words.
Having said that, issues fixed in 7 often still need backporting/testing/reviews against Drupal 6, and there's not a one-click way to see those issues at the moment, which is what http://drupal.org/node/221510 is for.