greatest hits albums don't work too well these days imo. people don't buy cd´s very often so why should i buy a cd with old songs i already have? i hope it will contain something more, like a dvd or something. (and the remix of my plague don't counts :P)
I think Greatest Hits are mainly produced to almost introduce people to a band. Get their "best of", find the tracks you like, and go into those individual cds.
Seeing Slipknot live is on my bucketlist. Love their dvds