If you read the release, each spreadsheet gets to run in it's own isolated container in a hypervisor system. You literally have separation of information at the file level, which is good. But I absolutely agree with you that if you store things in the cloud, you don't own those things, you give them away and lease that access back under restrictive terms. I don't find it to be worth it, but countless other people disagree with me.

If I'm to get on my soapbox after all, I'll just say this: Use json or jsonl, use polars, use jupyter and seaborn/matplotlib-pyplot, keep your data lolcat, and never open Excel again.

Edit: unless someone sends you an xslx and you need to convert it to csv before you transform it to jsonl. If someone has a cli that'll turn xslx -> jsonl directly I'd be so happy.