So Bitcoin has always used proof of work as did Ethereum. But with Ethereum switching over some of us must be thinking of the possibility of Bitcoin doing so as well at some point. With that in mind I wanted to revisit this topic as I remember there being a lot of criticism of proof of stake with the arrival of the first coins to start using it, but I don't recall the specifics.
One thing is we know that with proof of stake no actual work is required for the validation which secures the blockchain. Is this a concern or does it not really matter? What do you think are the other risks or concerns?