I have no experience operating one. I bought one a few years ago from someone who didn't realize (I think) what he had and couldn't use it on the older tractor he had. I quickly found someone who need it more than me and I sold it.
They are not like to old sickle bar mowers in that they actually have the cutting sections on two rows and cut easier, faster and do not get clogged up with clumps of grass. You can also cut with the bar in any position, horizontal to vertical. Need hydraulic connections to operate.