I liked DoC, save for the fact you have to be Vincent Valentine.
Unfortunately, I dislike him very much.
However, I do like Weiss the Immaculate and the rest of the Tsviets --
excluding Rosso the Crimson.
Back to the point, I do believe DoC would be worth buying if you like Vincent
Valentine and FPS, or just shooting games in general.
To be as honest as I can, I do like the game, but you could probably just
borrow it from a friend and get the same thrill -- if there even is a "thrill" to
go through. I guess it all depends on your likes for those types of games.