Overall this is a very convenient place to stay. Its about a 5-10min walk to Omori station and you can take the JR Keihin Tohoku line to get into the main parts of Tokyo.
The Good: Location is good and the area is very safe. The inside of the apartment is very modern. There is a Don Quijote about 2 minutes away and also other grocery stores and shopping near by.
The Not So Good: I booked this place for myself, it probably would be ok for 2 adults but a little uncomfortable. 3 adults would be probably not be a good idea.
The way the bathroom is configured leaves little room for privacy, especially is you are sitting on the toilet. The bathroom door is frosted and there is a gap under the door.
Although it wasn't a problem for me, if you are a light sleeper, noise maybe an issue here. The train tracks are basically right outside and from about 4am till a little after midnight trains go by and you can hear the track warning alarms. This unit was on the ground floor, so the building in front absorbed some of the noise, I would imagine it would be worse on the higher floors.
The kitchen is very small, it's ok for light meals but nothing more than that. It's not stocked with any oils or seasonings so you will need to pick that up at the nearby Daiso or the Don Quijote. Also while I was there, there were no bowls, only plates, cups, a pot and pan, and some misc utensils.
If you plan to do laundry, be aware that there is no washer in the unit. Instead there is coin operated machines in the building The only people I saw using the machines were the cleaners in the morning. You might want to keep that in mind if you are planning to do laundry.
Lastly, the cleanliness of the unit was not the greatest. Shower curtains were moldy, air conditioner was dirty, and misc hairs on the ground. The inside is modern and looks nice but small details seem to be overlooked. Hopefully this gets corrected.
Overall, the location was the best thing about this place and the price was the best in the area. There are some things that can be corrected that would make this place better. If you can overlook some of the faults its a good place to stay.