Not so because of monsters, but adventure parts. Very stressfull really. But when you really get into it, all you have is hours and hours of fun. Game is powered by Quake engine, and in the time Quake II was comming. Beautiful world created by masters in Raven.
Music is great and atmospheric.
Sounds - typical, but very cool. Like them very much. Raven has its own style of sounds that I like. Hexen II is the best action game I ever came across. It also has higher system requirements, so that may keep someone off.