Datis presents horror fans with a traditional, almost 'Mystery Inc.' concept filled with standard stereotypes, creepy setting and nice body count. Told with slapstick and satirical humor, the film is a fun treat. It is English subtitled (just in case you prefer your international films voice-over). The characters are well developed and charismatic creatures one expects to see in this type of horror movie, but they work and they are entertaining.
The special effects could have been a bit harder and more graphic-"Saturday Morning Mystery" done this sort of thing a bit better. I'm American I want a more visceral and gory experience in my kill shots. Still even for the more subtle choices taken to create the horror elements, "The Mansion" is still fun to watch. 
Overall the movie is a nice watch. It is effective in giving a creepy, horror throwback experience. The funny is funny and the horror is classic. It is a bit grosser than it is scary, a total New French Extremist fan film. Not good for the gore hound crowd, but still a worthwhile selection for most horror fans.