Everyone's pretty much said just about everything there is to say on many different views, but...
Personally, it is one of the greatest, if not *the greatest* single title in the PS2 library. The art, the soundworld, ambience, style, story up until that almost-very-ending part (you who played know what that is), but at the final boss it becomes great again.
Combat is one of the things that keeps splitting people and their opinions. On one hand it's repetitive with the two-button combat (yes, I said *TWO*, remember the alternative weapon and their functions) and Mist brush power. Then again they have many enemies that have alternative ways to be killed through the use of powers.
Environments... Gold. Solid gold. There are many places with their own style and music, looks and feel and whatnot.
And all in all, it is/was Clover's swansong, and what a beautiful one it is.
Buckle up, it's a long, *long* game though.