Just finished this. For what it was, a tiny handful of episodes covering more of prequel to the real story than the story itself, it was quite good. I love that they used Dracula's Curse as the basis for this, it's probably my second favorite Castlevania game ever (after Symphony of the Night, a masterpiece of videogaming).
The animation could definitely be better. Compare this to say, Netflix's Voltron: Legendary Defender and you can clearly see this isn't up to the same level. But holy hell is the voice cast amazing. Richard Armitage, always a favorite of mine, brings Trevor to life wonderfully. He's weary, beaten, angry and yet ultimately heroic. And James Callis does absolutely right by my favorite Castlevania character.
I'm already looking forward to the second season. Heard it will have 8 episodes instead of four. Hopefully that means we get a bit more story next time out.