I've played and finished Arx Fatalis and I have to say that it is only an average game. Unlike sprawling environments of RPGs like Oblivion the level design is very tight and there's always something interesting. The environments are also fairly different. Sound is also well done and feels very appropriate.
Unfortunately, many aspects of the game that try and make it immersive such as combining raw ingredients to make food come off as unnecessary or repetitive after a while. For example, there is no short cut to making food even after discovering the ingredients. So to make more apple pies, you have to manually mix dough and water over and over again. There is also no place to store items so I ended chucking everything in an empty room and making a huge mess. The same problems go with spell casting, you have to manually draw runes in the air to cast spells. Again, this is suppose to be immersive but just ends up annoying when you do it for the 50th time.
Sword fighting is extremely simplistic but normal attacks are pointless and you have to always charge your attacks to deal any real damage. And most goblins and humans take at least 3 or 4 fully charged attacks before dying. It came to the point where I wondered why the developers even bothered letting you attack without charging up.
I am perhaps judging it harshly and overall the gameplay and atmosphere is fairly well done considering the limited resources of the studio.
If you play the second game by the studio "Dark Messiah - Might and Magic" you'll notice some of these criticisms have been addressed. For example, learnt spells can simply equipped and can be cast with a single click and you no longer need to cook food so Arkane have obviously taken on board the criticism.