I'm not a big fan of Windows, but I'm a bit sad that the project didn't go anywhere forever and then was cancelled. They had some pretty ambitious and interesting ideas for it.

E.g. the only public beta of Vista that had it enabled used the database as a backing store for Outlook contacts. Each contact was an object in the database. So were photos. And you could link - as I recall, I only read about it back then - people to photos. And then search on that data, of course. Like, "give me all emails, documents, and photos that have to do with person X, from 2022-2023".

But IIRC, the performance was atrocious. They might have been able to fix that, but instead it ended on the junk heap of unrealized ideas.