I landed a massive database upgrade on a payroll system years ago, end-to-end standardization, cleanup, and improvement with a seamless rollout.

Our back clapping was interrupted by an angry customer phone call. One of our customers had gotten access to our internal schema and had a massive reporting setup in Access solving most of his needs.

I ended up converting his reports using some internal tools we had. Customers will grab anything to give them.

[The caliber and depth of his reports were such I wish we would have bought them instead of making me spend months building out our own reports.]