This is a big house - three floors and a basement. There's a lot of people, so this is pretty much a boarding house. However the place is run very well and there are people coming to clean up the whole house professionally on a regular basis. So cleanliness is quite good.
Noise levels are quite acceptable as well - incredible considering the number of people. If you want the quietest place look for the top floor (especially room 303).
Obviously the common areas and the kitchen can be rather busy in the evening, but I didn't have any problems with anyone - people staying there were very nice.
Ultimately, if you want to stay near York University / Seneca @ York, this is a fine choice. The rooms are clean and nice, especially on the 2nd and 3rd floor.
The host is very quick at replying and is very helpful, so you can ask him if you have any questions.
Overall, highly recommended if you don't mind other people around.