this game has some severe issues with structure that really bogs it down from being genuinely good. The premise is insanely good but it unfortunately fails to live up to what was put forth by the source material (A set of novels and Drama CDs). However, important characters such as Mayuri and Daru have a lot more to actually do in this game (Daru isn't just a joke, Mayuri isn't just a plot device, hell even Amadeus doesn't spout generic tsun lines), and as a result are significantly better than they are in base S;G, as well as the inclusion of Maho (Maho is good).
If you're going out of your way to finish this game, please watch the anime after.