I had used dkim-milter for over a year. This milter was pretty good but due to its phasing out, I had to switch to opendkim. To do the configuration was pretty easy as I had gained some experience in dkim-milter. Up to now, I still have no idea the percentage of my dkim-signed outgoing emails being permitted as reputable sender and not treated as suspicious spam. The fact is do it. If Facebook, Gmail, Yahoo all do it, why hesitate not to follow suit.