Few to this day. Bitcoin had more challenges when it was commonly considered a ponzi scheme that was only used to buy drugs on the deep web and gamble in unlicensed casinos.

Nowadays it is already widely used as SoV and more and more, although I would say that it is still used much more for payments than for example gold. But as the price continues to rise I think the trend towards use as SoV will increase.

As of today there are few challenges, as it has been regulated for sale and use in most countries, and if the USA were to create a strategic reserve of bitcoin, which implies a use as SoV, it is normal that other countries would start to copy it.