Different Drummer has had a short but dramatic life on iOS. First it was released at $300, simply to hold onto the name and discourage purchases until it was finished. Two weeks later it was re-released at $150 when the developer thought it was truly ready. I had contacted him to ask for a promo-code for review, but he said that he didn't think it was quite that ready.
Apps4iDevices bought it out-of-pocket and posted a little demo along with a write up about what it actually does!
From the article on Apps4iDevices:
It does have a big price tag for the app market, but after using it for a while I can tell you that it simply goes further than any other drum machine and gives results that I've never achieved before. I've used it for both drum patterns and synth parts, creating patterns that were beyond my expectations and imagination. This may seem too good to be true, but it's easier to appreciate when you understand the concept behind it. The real power of this machine is based on wave shaping using additive synthesis, combining the fundamental frequency with other partials to create a more complex wave shape. This wave shape is further manipulated by an additional set of rest, tie and dynamic waves.
Check out the full article for more details. This gives a much better idea of what this app is than the iTunes description about some "patent pending Cyclophone Technology" nonsense. I'm very interested in this after reading Apps4iDevices additive synth analogy.