I typically stay at higher class hotels in Tokyo, but had to get here for city overbooking. THe Celestine is not the fanciest hotel, Pool and Gym are absent, but rooms lack nothing compared to those I go to in 5 stars hotels (especially amenities). There's a fine lounge and personell is kind, with good, very good English (also the cleaning team, I found out).
The GrandRock restaurant deserves a special mention. Nice architecture, some less fancy details, but the chef displays excellent european selection. It's not the busiest in town, probably, but this restaurant deserves high ranking for food, dressings and service. I rarely am surprised by what is offered, but here I had two fully regenerating dinners.
To sum up: not the fanciest, but a safe, decent well located option.

Celestine is a top 4* hotel (don't expect 5* facilities). I was positively impressed as I ended up there- sceptical - during the busy IMF week and our usual corporate hotels were full.
Good location, Nice lobby, friendly staff, nice well equipped room with decent size for Tokyo standards. The bed was comfy, the view through the big windows very nice. I had north east facing and could see the Tokyo tower.
There is free wifi across.

Highlight: there is special filter coffee package available something I haven't see elsewhere.

Only downside? There are not linked with any frequent flyer programm.

I did not try breakfast.

My husband and I stayed at Celestine Hotel for 4 nights while we were in Tokyo. The hotel is a short walk from Toei Shibakoen Station, as well as Mita Station (exit A10 / A8) which has both Mita Line and Asakusa Line. Hotel staff spoke reasonable English, and were all very helpful. Their breakfast buffet was excellent both in terms of quality and choices!!!

To save some transportation costs, my husband and I bought the 1-way Airport Limousine tickets with Tokyo Metro 1-day Passes (promotional price, about 400-600 yen off the full price). The Airport Limousine dropped us off very conveniently in front of the hotel. (The Airport Limousine tickets alone is 3,000 yen per person, but if you throw in the Tokyo Metro Pass, and but them as a set, it only cost you 3,100 yen per person. There might be a minimum purchase of 2 sets, though.)

I stayed here for five nights while attending a conference at a nearby university. The staff were very helpful and spoke reasonable English. My room was a superior double on the 17th floor, I had a view of the building opposite with a bit of Tokyo between it and the next building. But even that was amazing from the 17th floor. My room was plenty big enough, with table and chairs, TV, huge comfy bed, big bath, and a fair bit of space to unpack into. Reception provided me with an adapter so that I could plug my laptop etc in, and I had free wifi. Breakfast wasn't incredibly good, but it was incredible, for the weird mix of food on offer including salad and pasta dishes. I'm told the Japanese breakfasts were great, I was happy enough with my eggs and toast, and cereal. The bar in the hotel is quiet but really enjoyable, and the Japanese gentleman I met there told me that the bartender is famous. There is a book of cocktails in the bar, and the barman is in the photo on the back. He makes good margaritas, and there is a large whiskey selection which my friends made headway with. As a solo traveler, I had an enjoyable meal in the restaurant on my first night, that's the last time I had western meals as Japanese food turned out to be amazing. The hotel is really well located, because its only a short walk from four different train lines, and in around Mita there are some great little restaurants, including an outstanding Ramen bar which I would direct you to if only it had an English name. I've try to put a photo of it up, and a map, so you could probably find it if you want an adventure. I had the special dipping Ramen, it was just amazing. The next afternoon we went back for Gyoza, and they were the best dumplings I ever hope to have.