Personally, I believe that the company is overvalued at 86 billion. Even if they were to reach that valuation in 5 years, from an employ compensation angle, one would make about the same if one were to work at a public tech company.
To add to it, they are fairly small and will likely be chaotic with low work life balance.
Considering all this, will you advice someone to join them now?
If it turns into a total screwup I think they'll have some good stories to tell. I'd rather hire somebody who left OpenAI than someone who left Google. (e.g. you probably learn something at OpenAI you can take with you, at Google you'll learn how to use their internal tools so you can get stuff done with x0.1 productivity but you certainly can't take the monopoly profits they make with you)