Well, statistically, I can listen to it twice a day which is a definite no-no with everything else that Emperor recorded. I'm getting tired of In the Nightside Eclipse. How many times a week can I get flung into the sludgy abyss of nocturnal darkness and despair before it gets on my nerves? Not more that once, I reckon. Prometheus has something to offer that no other Emperor album can-- it's fun.
It has some minor problems with flow, but in a nutshell, it's a technically impressive and ambitious album. So it's not pure black metal. Still great for what it is.