It kept war out of central Europe from 1945 until 2022 (I'm not 100% sure we shouldn't count Georgia/Bosnia/Chechnia/Kosovo, so I'll say "central Europe").

I don't think two nuclear armed powers have ever declared war on each other - despite two nuclear armed powers currently being in active conflict (India and China) and another few being incredibly geopolitically unfriendly (India/Pakistan and Israel/Iran).

The whole idea behind MAD initially was that if Russia decided to get ideas in Europe, the Western powers would stop them with a nuclear curtain. That's why France has a "warning shot" nuclear doctrine, and the US hasn't ruled out Nuclear First Strike.

IMO, for what it was trying to stop, it worked. Ask people in China and India - it seems to be working for them as well.

EDIT: as an amendment to this: would Russia have been so bold as to invade Ukraine if the 1994 surrender of Ukraine's nuclear arsenal hadn't happened?