I didn't know what to expect going into this game, but so far I'm pretty into it, I've played about 6-8 hours. Fair warning though, you really need to be into H-scenes in order to get the most enjoyment out of this game, as there's a ton of them in this game. Additionally, being into darker fetishes such as rape, would also be a plus, as if you're not, you'll probably have to end up skipping a good chunk of the h-scenes in the game. Also, there's a ton of weird fetishes (although nothing out of the ordinary if you're already into doujinshi, etc). But if you happen to fit the requirements this is probably one of the best eroges I've every played.
The story is pretty basic, but it's enough to keep me going from scene to scene. The characters are surprisingly interesting although archetypical. The real meat of the game is the h-scenes which are very well done when compared to most other eroge. The key to having a good h-scene is to frame the scenario well. Two people just having sex is exceptionally boring, and the game does fairly well in keeping the dynamics fresh and interesting. One drawback (although with the amount of h-scenes in this game is kind of expected) is that many CGs are reused, although the game does have different dialog. To give you an example, in order to upgrade that stats of your heroine, you have to give them a specific training (which is sexual in nature). There are three levels in each training, which are generally based around a specific fetish. So for the first training, is just plain old sex. There are two CGs associated with that training. So you'll unlock those CGs the first time you do that training, however when you do the level 2 and 3 of that training, you'll get the same CG. On the bright side, the scenario that leads into those scenes are different for each level.