I'm a little confused as to what you're asking actually. Are you asking about the larger cyclones (2, 3, 5HP and up, induction type ones), or the small ones that are available now that hook up to a shop vac?
I don't know much at all about the little ones, but the larger cyclones have been around for quite a while. I'm on my second one now. I'll never be without one again, it was one of the best purchases I've ever made. The large cyclones and the CT "extractors" (shop vac style) are two entirely different animals. A large cyclone is meant to move large amounts of air and lots and lots of sawdust, chips etc. Mine has a 55 gallon drum on it and there are days when I'll empty it 5 or 6 times in 8 hours. It sounds to me like you're asking more about the vac type.
For what its worth, I have one of the Dyson vacs and think it was a total waste of money. Its better than the Hoover, Eureka, etc types. However, I have a woman that cleans my house on a regular basis and she brings her own vac with her. It puts the Dyson to shame and then some. I believe its some type of Industrial Oreck or something like that. Its a good bit different than the ones you see advertised on TV and so forth. She said it cost about a third of what the Dyson does, yet it runs circles around the Dyson. We have two large dogs that shed a ridiculous amount of hair, a cat, one slob (me), and I'm also creating quite a bit of dust from doing home imporvements on a regular basis. Even with all that, she does the house in very little time and there's no dirt at all when she's done. I can run the Dyson right after she leaves and I'll end up with a completely empty canister on it. The Dyson is okay, but there's no way its worth the money, IMO. If mine broke tromorrow, I wouldn't buy another one.