Would be quite useful to have, when you have overlapping fact datasets in a single app, and need to make sure only one of the data sets are selected (and thus included in any sums, averages etc) at a time.
I wouldn't say that Robert. You could always set variables in Sense through the load script as per View, In 2.1.1. you now have a screen to manage this but for users to interact with the variables e.g. setting them yourself in the front end you still need to use an extension like qsVariable. I was hoping Qlik would have released a standard control for this but still on the wish list.
In the mean time qsVariable allows a certain amount of dynamic manipulation of the charts displayed by the end users themselves.