I am also not a fan of COF, even though I have tried. I can not get over the voice, the attempt to sound epic, and the overall silly image they try to convey. Some bands can act evil, and you almost believe it. COF just comes across as kids who were picked on in school, trying to act tough now. I have never been able to take them seriously.
As for Dimmu, I lost respect for them because of the synthesizer work. I felt Stomblast was a decent album, with a lot of potential. Their music just went downhill from that. They seem to borrow heavily from to many other bands. I swear at times I can hear Dark Tranquillity playing in some of their songs. When I first heard Enthroned Darkness Triumphant my reactions was This is not bad. After another listen I started to hate it. Ultimately I found the album to have a very strong opening song in Mourning Palace and ends with a decent song. Everything in the middle just drones on to much, sounding the same. Someone above mentioned their hate for synthesizers. I do not hate them, because I love some bands that are all electronic, but I agree that Dimmu does not know how to use them. It is the SAME playing for almost the entire middle of that album. "Baaaa ba ba ba baaaa baaa ba ba ba baaa"...UGH...
When their next album came out, I did not buy it, instead choosing to listen to a friends. I gave it back to him the next day. While I hear that their newer stuff is better, with more variation, I have yet to even try it.