It's good but it's not that great of a sequel.
First off, the anime movie intro... My god!! What have Konami done?!!! They have created an abomination! Two abominations actually, the second one being Portait of Ruin. I like anime don't get me wrong, but when they make Castlevania series, with its gorgeous character artwork into anime style, really ruined the whole artistically unique aspect that makes Castlevania. I loved the original artwork of its predecessors, but now the anime style they adopted left a hollow, blank, empty feeling of ruin. That and the fact that the anime really looked blotchy for a DS.
The story was good enough, with the good extensive use of previous characters from C:AoS. The music was good much of the environments were really well made right down to the smallest detail. Like for example, when you jump on top of a car covered in snow, the snow actually fell off.
The monsters were good but a lot of the monsters from C:AoS had some makeover animations and style, with some recurring monsters from C:HoD. But let's face it, I really don't like its look just because I prefered C:AoS with its extra sharp, clean, contrasted animations. Even some of the monsters like Iron Golem were cheap.
The difficulty I have to say was far too easy, even completing it through Hard mode posed no challenge. As for the souls, some of the monsters you have met through C:AoS now have different effects that the imp monster with its HP/MP switch was actually useless. So much so that you couldn't have the same effect like Killer Mantle of AoS applied to Iron Golem of DoS. While most of the souls effect have differed, there were some that actually made comebacks and improvements as you accumulate the same types. Like Persephone with its HP vacuum-like souls improved images but not effectiveness.
The items you collect are not as effective at times. They dumbed-down the best sword in the game, the Claimh Solais. Although you can make new weapons by using you souls, or release your extra souls. But who would want to do that, when accumulating them actually increases the souls' effectiveness.
As for the soul gathering, it was much more unbalance. It was actually harder to collect all of the souls. Either my luck sucked or that the game was programmed to be that unfair, I'll never know, I gave up along the way. It got to the point that I already leveled up to the highest possible level there was at 99 and still I was nowhere near getting 90% of the souls.
It was definitely a dumbed-down, watered-down experience for a fan-girl loyalist like myself.