TL:DR An excellent place to stay that's clean, comfortable, and literally just across Exit B3 or A1 of Oshiage station. Downside is that there are no fitness facilities if that's important to you. Buffet breakfast is also very good, and the voucher can be used for in-room dining which is also provided by Sizzler.
I stayed here for work and chose it due to it's location near a train station that has direct access to Haneda Airport and where I needed to be for work. The 2 nearby exits both have lift access so luggage is not an issue.
There's Life supermarket (2.storeys) just below and Nitori if you're into home furnishings, with Tokyo Solamanci with a full range of shopping options including Uniqlo and Loft which are my trip essentials.
The room itself is well designed, efficient and comfortable. It was generally well cleaned but I noticed some stains that remained there throughout the week I was there.
Perhaps my only complaint is that all your bathroom essentials have to be obtained from the lobby which is troublesome when you realise you've run out of something. Another bug bear is that they don't replenish your coffee in the room and I had to constantly request for these. Once when I asked, I was told to get it myself from the lobby. Last, they have a rigid cleaning policy to clean every 3rd day, which may not make sense if you have had the room cleaned the day before.
Otherwise, this is a great hotel that has many positives and I would highly recommend it!