Although I never actually finished the game, I managed to get to the final chapter in Risen before giving up on it. While it's a decent RPG there are quite a few glaring flaws that ended up making me lose interest in it.
While the voice work is excellent the characters themselves are pretty bland and uninspired. The story is pretty weak too (it starts off pretty interesting, especially when you're picking one of the factions to side with, but it just starts plummeting by the third chapter). A lot of the sidequests (and even some of the main quests) are pretty boring and the dungeon crawling can get pretty old pretty quick later on. And although the combat can be pretty merciless a lot of the time once you start getting used to the system, leveling up and getting better equipment it starts to get easier. Finally, I think there were far too many dungeons and caves, and not enough towns. It may seem a bit silly, but I like to have plenty of NPCs to interact with, not just mostly enemies and creatures.
Risen is by no means a terrible game (especially at a $15 price point). The combat system works well enough most of the time and the game has a lot of content. But the weak story, bland characters and repetitive dungeon crawling made me lose interest before I could finish it.