An excellent post by Ivan Pepelnjak, pulling all the unicorns down to earth:
Imagine you want to build your own F1 racing car … but the only component you got is a super-duper racing engine from Mercedes Benz. You’re left with the “easy” task of designing the car body, suspension, gears, wheels, brakes and a few other choice bits and pieces.
This is the current state of Openflow or any other SDN. I have called it earlier that Openflow is assembly which needs a higher level programming language to use it. But the premise goes even further; in today’s legacy networks these controllers won’t help you.