Do-C Hotel benefits from an incredible location—right in the heart of Tokyo without being too close to the overwhelming crowds. It is literally a two-minute walk from the station, making it extremely convenient, and the surrounding area is great for hanging out. The sauna is a definite plus, although after a long day of walking, I personally would have preferred access to an onsen instead.
The staff is very friendly and helpful. Even those who do not speak Japanese make a genuine effort to assist guests, which is appreciated. The capsules themselves are standard in size, and having the storage area on the same floor is a practical and convenient feature.
There are, however, a few downsides. The hotel has only one lift, which can be frustrating as you often need to wait—though if you are not in a hurry, it may not be a major issue. Earbuds are provided, which is thoughtful, as you are quite likely to be placed next to a snoring neighbor.
The main negative point for me was the ventilation in the sleeping areas. It felt insufficient, and there was a noticeable smell, particularly considering that many guests store their shoes outside the capsules. Unlike other capsule hotels, guests are allowed to walk into the sleeping areas wearing shoes, which likely contributes to this issue.