Overall, the property feels very impersonal, simply because it is too large. You will run into some not so courteous travelers here.
The lobby and restaurant need renovation, bad 80's style. Rooms are more modern but have no heat. It tends to smell musty and the windows don't open but they do provide dehumidifyers.
Bathrooms are the size of a cruiseship bathroom but clean.
S.P. is located at Seibu Shinjuku station, directly next to the Kabukicho nightlife district, which can be a bit seedy. Cross Yakusuni dori and you will enter a nice shopping and restaurant district. It will take you 10-20 minutes to get to your subway tracks, depending on which line you are taking, so be prepared to walk. A lot.
Lots of hustle and bustle in the area, so if that's not your thing, stay in Asakusa.
The hotel is very dated and smells a bit funky. Rooms are small and don't have heat, only AC.
Breakfast is served buffet style in the Viking restaurant. They do offer Western options in addition to the usual Japanese rice, miso soup, fish and pickles. For the price however (2,200 yen) the quality is not great. It was nice to have an omelet station, pancakes, salad bar and fresh fruit, but the pastries were not fresh and options generally limited.
The bell desk is always busy, but quite helpful. They were able to book me a hair appointment at a very nice salon and even translated my wishes to the salon owner while I was there. They also have umbrellas to lend, until they run out.