This is finally done. You can now compare with both dimension values and
time ranges as your dimension down the left side, including the ability
to align trend lines for comparison periods on the same graph.
@Stef: I believe this is still only in Ad Hoc Analysis. We are looking
at adding it to Analysis Workspace, specifically for the Flow
visualization. Other than that, I don't believe this is among hte many
features we are currently working on.