I have been using it for a project for half a year, and it has been wonderful. It seems very powerful and packs a lot of features. But I do not see popularity of it that I think it deserves. Not here, not on the internet, tutorials are limited. Maybe I am looking at wrong direction, anyways. Do I over-estimate it or is it really that good but only a few people know it? It is even supported on Windows with Hyper-V virtual machines.
http://openvswitch.org