I don't like Circle of the Moon.
I recently started an LP on it, but not because I like it, but rather, it's the first Metroidvania-styled CV that I ever played (My family owned Symphony of the Night before we had Circle of the Moon, but I was young, and too scared to play it.). I owe it respect in that regard.
Having to double tap to run all the time has to be one of the most grating things ever. The only game I know that makes double tap-styled running stupider is Kirby's Dreamland 3, where your running speed, coupled with mediocre controls, causes 90% of your deaths in that game.
It also doesn't help that single rooms and the castle itself are enormous and really spacey. It makes you hate walking even more.
People say Portrait of Ruin has bad level design, but I think Circle of the Moon is even worse. There are tons of areas that repeat several times, back to back. relentlessly assaulting your brain with routine gestures like going up one of the fifty billion vertical chambers.
Challenge-wise, it doesn't disappoint, but it's hard to really enjoy the challenge when your character feels so stiff. Additionally, there are more difficult Metroidvania styled CVs with better controls (Order of Ecclesia come to mind).
The DSS card system is okay mechanics-wise, but what completely hampers it is the difficulty of finding the DSS cards, and the luck-based factor in retrieving them. Additionally, some cards have effects that only the most dedicated players will be able to figure out on their own. I still don't know how I managed to discover that a down forward up + attack motion makes certain cards take effect.
The game hasn't aged well. Pretty much everything done in the game has been done better somewhere else in the franchise, and the game doesn't have the benefit of being "balanced" in terms of quality like Aria of Sorrow.
So yeah. I dun liek it.