I studied at EF Tokyo over the summer for three weeks. Compared to other language schools in Tokyo, EF is egregiously overpriced. For the price you pay for a month at EF, you could get 2-3 months at another school of equal or better quality.
Riisa-sensei, my teacher for two weeks, was fantastic. Some other teachers seemed inexperienced, but teaching quality for the most part was good. My class moved through material at an extremely slow pace, however, so don't come to EF if your goal is to learn as much Japanese as you can.
Activities were alright. Most of them are not free. You pay for them using "activity credits" that you purchase. These activities range from museum visits to weekend trips, and are usually quite pricey.
I stayed in the "EF Residence" in Tama-plaza. Please be aware that EF does not own this building -- it's a share-house with rooms that can be rented by anyone. The quality of the accommodation was quite poor. I stayed in a bunk bed room that only had one tiny desk and one dresser for both my roommate and I. When I arrived, my bed was dirty and had food scraps on it. Thankfully, I didn't spend much time in my room.
The best part of EF was the people I met -- I made great friends with like-minded people from all over the world, some of which I still keep in contact with. With the friends I made from EF, I went on a weekend trip to Kyoto and climbed Mt. Fuji. I will forever cherish the memories I made in Tokyo last summer.
Despite its shortcomings, EF Tokyo is a good way to get your first taste of Japan. However, I would look at other programs with better value is the cost is too high.