If one hopes for a game with complex diplomacy, stay away. However, if one likes saccharine voice, go for it.
Alliances (a.k.a. partnerships) can be forged, although on most cases the alliance is forged early on and are very difficult to establish once your initial partner for the 14 days have abandoned you. You can also send tributes to other girls, including your partner, to strengthen your relationship (and the alliance) or to seek a potential ally. One must have an ally for the beach volleyball. However, one cannot check on the diplomatic stance that they have with you easily, save for attempting to give gift in the public (not on inn) or seeking an alliance actively by asking another girl, not to mention that you cannot check the stance that your own partner has with you, save for the beginning of the day. Bottom Line: diplomacy is largely underdeveloped in this game.
The game hosts a series of mini-games, which in most cases lack substance. Volleyball is seriously NOT well implemented, as the camera angle makes it difficult to accurately predict the location at which the ball would land. Controls are fine, and you can synchronize with your ally for devastating plays, but you will usually lose if you are new to the game. For money making, one engages in the Marina game, which is arguably the core addition and perhaps the most developed part of the game. One acquires points by achieving a rank and staying in course (course boundaries tend to be wide), but accumulation of used turbos must be done in a much narrower course. Rank is the greatest determinant for output, although following course and tricks add to a small portion of the output. There are a few courses in game: some are ridiculously annoying, while others are relatively simple. For other games, one must purchase a ticket, and those games are even harder, either because of high learning curve (as with the case of water sliding) or luck-based nature of the game (as with the case of tug-of-war and butt-fight). Casino is accessible in the inn, and it should be considered as extra recreation rather than a source of income.
Audio tends to be the better aspect of Dead or Alive Xtreme 2. BGM certainly is cheerful and quite well designed to fit the happy ambience of the game. Voices are also good: Gamespot considers it bad, but one more often than not enjoy the massively saccharine voice (particularly true of Hitomi w00t!) commentary by the character of choice (or other girls in games). If you are a big fan of cheery ambience and cute voices, this has both elements in the game.
Overall, Fine external elements are often negated by the lack of substance in most minigames and underdeveloped diplomacy element in the game. That was why this game was disappointing: The good graphical and audio elements would should be a support element, not a main element of the game.