It was once useful. And Kos says it will be useful again.
But for the moment (12:40EST) it's 92 spam messages and 8 truly needed to be hidden, but not spam, messages. That 92% useless number varies but never very much.
Right now the Hidden list is waste of DKos resources, both people and computer. And it's a total waste of time for users who go in the hope of seeing a solution in place and working.
All I'd like to see is an honest estimate of when the tech staff thinks it'll have a solution up and running.