I have used them a few time last year on my machine - very impressive attachment, and can handle everything you mentioned above. I like having it on a 3pt instead of a skid steer, but thats just my preference.
You have the ability to windrow the debris you speak of, and it is the best tool to just make old lawns look like new again. It works better, than a box blade, a tiller, and a yard rake. Imagine having them all at once, thats what a Harley rake can do, in one pass....must have the carbide teeth option to make it worth while.
If you cant get your hand on one, you can get really get good results with a tiller and a york rake....poor mans substitute but not a bad substitute overall. Im not calling you poor, so dont worry Harley rakes are expensive as heck 6k-7k easily, something that will need to be justified with work for me to buy one. Not there yet, and I can get by with what I have already, if need be.