One of the worst games in the series. Though somehow it's much closer to "Castlevania" than ASO and DOS.
Gameplay was generally rehash of previous games. Johnatan was very "Soma-like" and ultimately boring. Charlotte on the other hand was a breath of fresh air after all this countless "whip'n'sword heroes". I used her to complete most of the game. Johnatan was usually shutdown and off screen. Only times when I used him is to defeat first boss, Reaper and "Drac'n'Reaper combination". And obviously Richter battle since there were no choice. All other times I played as Charlotte and that was probably exactly what made me think of this game as a "mediocre game" rather than "horrible game" that POR had potential to be.
Quest were boring. I completed maybe like 20 of them and then stopped. In OOE I completed all quests and it is the only "metroidvania" in the series that I completed on 100%.
Partner system was crap. It was advertised gimmick that was really tacked in the game without any idea of how to make it relevant to the gameplay as a whole and not few moments in the begining and final boss battles.
Storywise the game as it is now is a garbage. There was tremendious potential to the story of this game to be one of the darkest and most mature in the series. But as it happens, in the darkest hour, IGA decided for whatever reason to retool potentially the best story in the series into animeish generic crap. Characters were degraded into idiots, new "villain" was barely there as well as Reaper and Dracula made his mandatory (and absolutely needless) appearance. Suffice to say the game made me whimp, because even now, there are shades of what could have been, if POR wasn't created with little children in mind.
It's still a bit better in story department than AOS / DOS, because it's actually have ties with the rest series and it's not just some randomness about japanese priests and the stuff.
Levels were mediocre. Dracula's castle looked like it was recently built. Or robbed. Nothing interesting at all and most of it's areas were generic. Portraits were a bit more interesting, but only because of the novelty, not because they had strong designs. Circus was ugly and disconnected, even more than areas in Dracula X. Wichtes school was boring. Egypt levels were probably the biggest WTF moment the series have seen. It was like they were ripped out of completely different game alltogether and put into Castlevania to spare dev.team inhuman efforts of creating some original area.
What really make me dislike Portrait areas is the fact that were doubled. Completing them once was boring. Completing them twice was like crawling through the mud. Reminded me about my time in the second castle in the SOTN.
Music didn't do anything for me. Most of the tracks were filled with generic DS clanking. Though I think, that unlike HOD, the music in this game was generally spoiled by it's arrangement, not because tracks were really bad or uninspired. My favorite melody in this game (and the only track that I seriously liked in POR) is "Hail form the past". Ironically it came from the first Egyptian level, so one can say that they weren't that useless after all.
Generally the game had potential. But it was all wasted to create some kiddy Castlevania game without much of the novelty or the inspiration. There were neat ideas here and there, but it was not enough to save the whole game from being mediocre.
And I agree with The Silverlord about the fact that LOS being balmed for being "not-castlevaniash" enough, while POR generally was much worse in that aspect (even if it's in continuty with the other games).