The biggest challenge is the ability to proceed number of transactions in a second or minute is too low for a system that is supposed to change the existing system. So Bitcoin is definitely behind the processing of transaction and that is the reason why we are facing high fee for a transaction to proceed so if the earlier gets a solution then there won't be a clog in the network and also high fee.

Volatility is also big challenge because we always wanted a monetary system to have stable value so we may not worry about the inflation, etc while this is actually benefiting the users now by gaining more value when they hold but from the perspective of money it is a red mark that needs to be resolved.