SDL is one of the best SDN controller I have used so far. The GUI is easy to use, and you can manage almost all aspects of your networking in this tool. I haven't found anything I really dislike about it. It's pretty much perfect for my needs right now! If you want an open-source solution, then go with this product. There are some things I would like to see improved such as more integration with other products and services (eg. vCenter). We have been using SDL for several months now and we are very happy with our decision. We use it to automate the creation of VMs, create VM templates, provisioning, and configuration of NSX components.