Being that I heard many great things about the series, I decided to pick up Portrait of Ruin. Boy, was I in for a treat!
Second reaction: holy crap, this music is GREAT! Now I've become a Castlevania soundtrack fiend. Very gothic instrumentation (or synthesizeation). Most of it is uptempo, using a strong forward motion to propel the gameplay, with more haunting or sorrowful tunes where appropriate. Favorite tracks: "Gaze Up at the Darkness," "Iron Blue Intention," "Crucifix Held Close," "Piercing Silence," "Dance of Sadness," "Banquet of Madness," "Bloodlines Bequeathed," "Thirst for Blood," and... of course... "Simon's Theme." Also, the voice action --- though few and far between -- is top-notch. Plus, the game looks great. Lots of top-notch sprite work, which is becoming more and more of a lost art. Here, though, it's in full swing. Everything looks great, from the hero sprites to the enemies to the backgrounds to the cutscene avatars.
After you complete the game (with the "good" ending), and also depending upon your actions in the game, there are lots of extra modes to give a whirl, including Richter Mode, Sisters Mode (which is a prequel to the events in the game), and a Old Axe Armor mode if you defeat 1,000 of those (yikes!). Also, two new boss rush levels are unlocked. The single-player is just oozing with replayability; however, the multiplayer could have been fleshed out. It's merely a co-op boss rush. Even though I love co-op, it needs to be more than boss rush...
Ah well. The whole package is really excellent. Out of everything I've played, this is the best game on the DS. Nothing compares in terms of a single-player experience. We'll see how that holds up when Phantom Hourglass is released. ;)