Strongly need the ability to construct calculated metrics that are not based solely on Metrics/Events alone but allow qualification by values in variables. This would let you more accurately quantify Segments of traffic, trend them, set Alerts on them, etc.
Example - You want to know the Percent % of Visitors looking at Cars vs. Trucks (stored in eVar1)
eVar1('Cars') / Visits OR eVar1(Contains 'Trucks') / Visits
Calculate the difference between Cars & Trucks = (eVar1('Cars') - eVar1('Trucks))
Better Example: You want to know how many people are doing a Product Configuration (Event1) for a given Segment of your Products (i.e. Cars)
Event1 (eVar1='Cars') / Visits
This then tied with See Also IDEA: % Based Alerts really opens up Site Catalyst to pushing out awareness of Segments shifting, dashboarding this, etc.