On Flame and Smoke, I've used Deal to do quick "timewarps" on certain types of elements, like, for example: I have a smoke element that was shot at high speed. The clip is about 30 seconds long. I want it quite a bit faster, so I might try different "deals", like 5, where one of the resulting clips will play 5x faster. It's just a faster process than doing an actual timewarp.
On another effect, I wanted a "stuttering" effect, where the clip ostensibly runs in real time, but the even numbered frames were duplicates of the preceeding odd numbered frames (in other words, like a freeze frame every two frames. There is a Sapphire spark that achieves this effect, and nowadays you can do it in CFX by using 2 timewarp nodes.
To be sure, it has limited usefulness, but when you can use it, it's quite fast to render.
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