Even in the best situations, contrast detect autofocus has to hunt, by its nature. It needs to focus beyond and then snap back, and this occurs every time focus needs to be set/changed. If something is moving, it will do this continuously, and while it can be good (I have only tried it on the gh2), it isn't something that you would want to rely on for fast action. Continuing off of that, if it is something you can't rely on, then you likely won't use it (for risk of ruining the shot), it would therefore essentially be a gimmick.