Do you think Dimmu Borgir's musical quality has decreased?

So, I have been considering one of my favorite band's discography. Dimmu Borgir has stirred a lot of controversy with their latest release (In Sorte Diaboli), and I can understand why. I bought the album (mostly because the imagery looked awsome), and haven't been fully "disappointed", however I am not entirely happy with it either. It seems to be lacking in comparison to an album like Stormblast or Death Cult Armageddon. The synths/keys have really stepped back, and most of the time they are only used as filler parts. The guitar playing is okay, but for being a very guitar fueled album the guitars lack, alot. The only songs to even stick out to me were the ones with Vortex's singing voice included. So, how do you feel? Do you think Dimmu Borgir's music has gotten stale, or minimally has decreased in quality and value? What are your favorite Dimmu Borgir albums? Songs? Why?