Curse of Darkness is one of those games which you'll like, but still will hope it would have been better.
+ Gameplay is good. The combat, the selection screens, everything is which requires for you to push buttons has been made well. The combat especially is balanced between easy and challenging and offers many ways to battle foes.
+ Music is awesome. No other comment. The cream of Ps2 games' music.
+ Voice-acting is surprisingly good. The actors are top-notch, too bad you can't watch the game's cutscenes anywhere except in YouTube.com.
+ The improvement over Lament of Innocence is notable. All the new weapons, new elements to combat, better cutscenes etc.
+ The setting (story) is your little-better-than-average- Castlevania style. I'd say it's better than in the Lament of Innocence, not by a whole lot but still. It's ok.
+ The graphics are ok too. Nothing too special but satisfying.
- The level design is the curse of this game. The levels quickly get boring, and you'll constantly use Hector's (the protagonist) evade-move to move even slightly faster. The level design literally kills the game's potential fun factor by half.
- There's not much to say on the side of level design. The bosses are ok, but the enemies are quite cheap sometimes.
Special praise: The outlook of the game is superb. Cover artwork is magnificent, the graphics are ok and the music is godlike. (They must have spent too much time on these factors rather thatn the level design.)
Curse of Darkness could have been the greatest 3d-Castlevania to date, but the cursed level design banished the fans of both action and Castlevania games. I'd still recommend it to anyone who wants a decent game with good voice-acting and music. Oh God, the music is incredible.