Namnso Ukpanah
Namnso Ukpanah reviewedDesign SystemsLearn and engage in the craft of building design systems
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Pros: 

They are a living style guide

Cons: 

Not really a con but getting your team to see it might be hard.

I already did here.

https://www.designsystems.com/stories/q-and-a-with-nanmso-pt-1/

Namnso Ukpanah has used this product for one year.