SEPA has been a good thing for Europe, but I know some EU countries still don't use SEPA. It allows us to make bank transfers free of cost and quite fast. Sometimes less than 12 hours, so fast too. I personally don't see any disadvantage other than the bank is still able to identify the sender/receiver and can too decide to lock a transfer.
I know some third world countries which have bank transfer methods like IMPS where money is sent to a destination within minutes. They also have high transfer limits. I like SEPA but taking more than 24 hours to reflect payments is a turn-off. Like why can't they create a system where money transfer is instant? The security issues aside but if someone is really in a need for cash in another European country, there should be a way out using SEPA.