This review is for a normal, single person, room with bathroom, not a capsule.
You get exactly what you pay for. A room to sleep in and a bathroom for hygiene and a toilet.
These rooms may be small, but they are worth the low low price you pay. In the room I had enough space to keep 2 pieces of luggage, which were not small. Provided are TV, a Hair Dryer and a Water Heater.
There is one outlet in the room with place for 3 things. The hotel uses a 3 way splitter and occupies all but one outlet. So if you want to use your stuff I highly recommend getting a splitter for your devices beforehand. If you come from a country with different outlet type, get one adapter and like a 10-splitter and you are pretty much set. I was able to charge all my devices over night every time.
Rooms have one window which can be opened. Should it be too cold a heating element is also available.
All this is in my opinion worth the price alone, since it is pretty small, but so is the price. Here is what tips this to being awesome, though. You room gets cleaned EVERY DAY. Sheets are changed, you get new towels, garbage bag is changed, everything. For this price I did not expect that! Also you are provided a toothbrush, razor, soap and shampoo. The last thing that I LOVE about this hotel is the laundry service. For a mere 400 yen you can wash and dry your laundry. The machines are BIG so it can handle 2 weeks worth of laundry easily.
For these reasons I think Asakusa Hotel Wasou is one of the best.