Alright, I've got the game and I've played about 20 minutes in so far.
The frame rate is not just horrific, it's a freaking disaster. They said this game was downgraded to 30 frames per second to preserve the graphics. Well, the PS2 can't even seem to keep that up 98% of the time, and seems more like 15 FPS or less (literally!). It's unbelievably choppy, and just feels really sluggish.
Seamless loading is no more. there's a very noticeable extra second or two between loading areas and battles. Likewise, memory card access is a ton slower. Takes about 6-7 literal seconds to save. It was lightning quick on the gamecube (only took 1.5 seconds).
Character models are definitely more jaggy looking. Background graphics don't seem to be as detailed but I could just be imagining things. I'll make some screenshots of identical points later and compare them.
The music... I noticed some slight differences between the way the music sounded in the GameCube version compared to the OST. The PS2 version actually sounds a lot closer to that of the OST. It's pretty faithful. I think it's safe to say that the new ToS OST coming out next month will just be a reprint of the original, since there's no reason for it to sound any different.