Completely off-topic: some years ago, an Excel on steroid was posted on HN. A UI where you could visually organize your column groupings, your multi-cardinality (one cell of one column had several connecting cells on its next column), your drillDowns.
Is there an insightful fellow here who remembers a tool like that, and could remind me the name of it.
It was really food for thought about how the proper UI can properly drive your mental model about data [or kill it, in the case of Excel]