For me HoD sucks and yet it doesn't suck. The castle environments were definitely a few steps up from CotM however there were some distant backdrops beyond the backgrounds that felt cheap and rushed. Like the lava rivers to name one such backdrop.
Juste overall does not come off as unique to me. He very much resembles Alucard in Belmont form. From his white hair and tailcoat, to his pale skin complexion. That, and leaves behind a blue energy streak like Alucard does. I think much more thought could have gone into him rather then virtually cloning Alucard's design.
His whip was a tad too short. Kinda reminds me of Sonia's whip. Why are they a tad too short? The vampirekiller isn't a short whip, it's got range and it's very deadly when it hits something. At least CotM had range.
The magic system was far more limited then CotM's DSS system. So much so that, to be honest, I've never even used it. I got more enjoyment out of LoI's magic system and it's almost the same concept with regards to the sub-weapons. And in LoI you are almost forced to use it if you want to survive certain fights. An example would be against the Forgotten One.
The Music...sadly due to the limited space on the cart at that time it had to take the big hit. Is the music in HoD better then CotM? Personally I'd have to give this a definite no. Sure CotM has reused tracks but at least they are decent and even catchy which helps to keep one engaged in the game. For some reason HoD's tracks almost make me feel board and that has absolutely nothing to do with their quality either. I don't have a problem with chip tunes so long as they're engaging and catchy. HoD just didn't do it for me. The better attempt was done in AoS and that game could afford better music quality.
The sounds were good. No question about that. Although I think that was one of the reasons why the music quality had to take a backseat. There were also some brief voice clips that also took away from the music being better then it was.
The animations for the characters (Boss armors mainly) were animated like they were in SotN and I also feel this lead to the lack in music quality. Sprite Vectoring would suck up a lot of memory if I'm not mistaken. Juste's animations, sadly, were not as smooth, nor done well as they could have been. He looked awkward to me. Nathan's animations in CotM (though more limited) were better executed and flowed more naturally.
The story here is nothing new. It's the old cliche love tale of two friends rescuing someone very dear to them. Although given my severe dislike for love triangles, this story isn't nearly as bad as most others (Judgement's being the worst for reasons I've stated in the past). The way it is done is more along the lines of good friends rescuing a very dear friend and we don't see the love triangle BS overtaking or overshadowing everything else. So IMO the story is passable for me. It's nothing new or groundbreaking but it works for what it is. Although I think almost everyone knows who Lydie eventually shacks up with and it's not Maxim. Sorry Maxim fans

The Mirrored castle was a bit of an odd duck. It's like the inverted castle but is not flipped on its head. This felt really tedious having to go through the same castle a second time. They didn't even give it it's own music to make it stand out. At least SotN's inverted castle was something that was just a little different so It kept me engaged enough.
Over all HoD is passable for me but it doesn't beat CotM with really anything new. AoS was much better at this and is, by far, more closer to SotN quality on a handheld.