Had a fantastic stay at Mei/Yousuke's airbnb in Shibuya! The listing included a lot of amenities, including tons of extra bed sheets, cleaning supplies, toiletries, hangars, etc. all located under the bed. Garbage was simply placed on the balcony - I didn't notice any smell related issues from doing this. The shower water was limited (300L/day) when we visited, but we never ran out of hot water even with 4 people showering daily. The kitchen is relatively well stocked and should be able to accommodate any cooking needs. Provided blankets/towels were good quality and the room heater/ac was a welcome addition during the cold winter months.
As for the negatives - this room is CRAMPED! The pictures do a great job of hiding how small the room is. When we arrived, my shoulders would nearly touch both bunk beds if I stood between them (I am skinny but around 6' tall.) We had to move the beds and furniture around to accommodate this. It is worth mentioning that everything seems to be smaller in Japan, so I bet this problem extends to other airbnb's - additionally, 4 bed listings seem to be sparse around those parts. It is also worth mentioning that their towel bar inside the (also very small) bathroom was broken with jagged edges, and 2 of our group members gave themselves nasty scratch/cut wounds on their arms from simply using the bathroom.
Overall, would book again! Perfect place for students or friends who don't particularly care about personal space, but do care about an excellent location and good nightly rate.