After reconquering Dracula X Chronicles (along with Rondo and the 'director's cut' of SotN) during the past couple weeks, I'm currently battling my way through CotM. I love the atmosphere of the game - like SotN had a baby with Super Castlevania IV. The Underground Gallery and Underground Warehouse both seem straight out of the latter. The gallery in particular had some nice detailing. I still have no idea if that's rust or something worse leaking out from those ram's heads mounted along the walls. Also, the Machine Tower is still the best clock tower since the old games, outclassed perhaps only by OoE's stage. The boss fights are still...well, boss. The Zombie Dragons, Necromancer, Adramelech, and Dracula's second form are tops.
Still, I wish some of the smaller areas had their own theme as Sinking Old Sanctuary gets old really quick. I wish Vampire Killer was used for a different area though instead of the largest stage in the game, or Sotaro Tojima should've looked towards the longer variant from the X68k game instead of Super Castlevania IV's. I generally like all the remixes, even its underrated version of Dance of Illusions. I just wish there were more original compositions, because they were all excellent.