"Freezing moon" is from "De mysteriis dom Sathanas" (unfortunatly not the original one, but the one on blue/purple vinyl) and that is their best album IMO, but then again I only have that and "Grand..." plus "Live in Marseille 2000".
Don't just trust "Grand Dec of war is one of my fav cds ever, i dont know why you would not like it, if you dont like grand dec of war i would not listin to any other mayhem because grand dec is there best one", as this is just a matter of opinion. I think you should check out their other work and as I said I think "De..." is their best and so do the majority of their fans too as far as I know.
As for "Grand..." I think it's good, but I think it gets a little ruined sometimes. The reason is Maniac's vocals. I think his screams are among the "lesser worse" in black metal (as I haven't heard any I would call good), but his clean vocals is misfitting! He sounds like a mix of a terrible white guy who raps for one of the first times in his life and an announcer at a boxing event! Sometimes it's so corny that you feel more like laughing than getting scared!
I don't know if I would call it the most innovative black metal album of all time, but then again I don't know which one I would say instead. I can't really come up with one (maybe there isn't any).
I don't really mind the electronics on the album. The electronic song is acceptable, but usually one I skip (the only one that I do that to).
The last song has crappy drumming IMO. Although Hellhammer is one of my favorite drummers, I think his drum work on that song sounds stupid!