I stayed in The Westin for a full week for a conference. During the week I made some short visits to different sights in Tokyo: The Imperial Gardens, Ginza ("Fifth Avenue" of Tokyo), Sensoji Temple, Akihabara electronics shopping, Shibuya for dining and shopping (both Sinjuku and Harajuku). Hotel location is great for this, as it's close to Ebisu train station, which is a crossroads for a couple of subway lines.
Hotel itself is good quality business hotel with nice rooms and good service. Breakfast buffet is wonderful with fruit smoothies and other extras you don't get so often. Consierge made a mistake with a restaurant reservation, but they were extremely apologetic about it afterwards.
Right next door to hotel is a shopping mall, not huge, but very elegant. They have Starbucks, if that is important for you. :-) You can take a limousine bus from Narita airport to hotel and back, which is convenient and inexpensive, but bus schedule needs to match your schedule; they do not run always so frequently.
Over all, I was satisfied with my stay a The Westin. And Tokyo is a lovely place: where else can you find a city of 10-20 million people that is so polite, clean and safe?