we use a variant of the PlanningGame with great success.  One thing that led us to it is that for us, ''Business'' is actually lots of independent Players with conflicting priorities.  We always use DateDriveCommitment, allocate each player some ideal time, and then invite them to negotiate with each other.  Getting out of this crossfire is valuable to us poor developers. --DaveCleal 
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Great idea and good way of putting it.  I have come to standardly recommend "fix the date, change the scope" as a basic survival strategy, but hadn't seen it from this perspective.  I'll strengthen my recommendation on this from now on (5/99). --AlistairCockburn