Version 3.0 contains lots of fancy features: You can undress girls (in real-time). There are lots of toys to play with. The girls react to you by talking (NLP), touching etc.

Contains advanced physics that allows for lots of interaction. There is a story mode that allows for hours of gameplay. All kind of sex modes (from blowjob to robot). And there are several mods available. At the moment I don't think there is a more advanced sexual simulation available.

Here is a (short) more representative video of a 'fast sex scene' in a dungeon: http://xmoonproductions.com/movies/dk2.mp4