Between all the SDN rainbows and Unicorns there are a couple of people developing and writing with their feet on the ground. Brent Sallisbury is on of those. In his latest blog he explains very well how to experiment with Openflow in an existing network.
It is hacking and developing at this point until the majorities vendors retrain and sell the products. Reference architectures will be few and far between since industry verticals have diverse needs, so will the solutions.
The message here is that if you start to experiment with Openflow in your campus network, not the datacenter, you are joining an elite community of engineers that need each other to solve challenges.
I hope this post is an example of the quality of the book on Openflow that Brent is writing. Knowing Brent, and Greg for the win, I can on forehand recommend this book to you.