I would describe Mark of the Beast as a dud. As far as Crystal Logic, which is supposedly one of their best, I was only really impressed by "Necropolis" and the title track. Nothing else really reached the level of awesomeness of those two.
I'm not saying they're bad. They've definitely done some great songs, and I intend to check out more of their albums. But I find it rather laughable that people here are putting them on such a pedestal. They seem to be getting idolised because of their underground status. Which happens with a lot of fucking bands here, I might add.