Rotary rakes are very good. I've used single and twin rotor wheel rakes. They do a good, tidy job. You can't run too fast relative to rotor speed, but that goes for pretty much any haymaking equipment- take it steady and it'll work well.
The only downside is that you have to be very careful working near field edges, especially turning at the field corners. You can be two feet off the fence, then a moment of inattention, (like looking where the front of the tractor is) and you hear clackclackclackclack and before you can stop the pto you've ripped out a length of fence wire and bent four of the arms... Keep the drawbar as short as possible. A massey with a 18" drawbar on a 16' wide twin rotor rake has some very peculiar steering/trailing characteristics.The same rake on a small tractor with the shortest possible drawbar and it worked like a charm.
Ross