First off, this really is a lovely medium to small sized hotel, set on a leafy, quiet street right near the Frankfurt "Messe" (Trade Fair), natural history museum, two U-bahn lines and several trolley lines. They feature a very good spread of cooked and cold breakfast entrees, cereal, fruit, scrumptious crusty, grainy breads, cereals, and excellent coffee (this is a real sticking point with me). The rooms are comfortable, clean, modern and well lit. If you like The Cozy, this hotel fits the description.
The staff is relentlessly pleasant, helpful and eager to please.
Here are my caveats, one of which is a cultural thing: there's no air conditioning nor even a ceiling fan. As a matter of fact, there were no ventilation grids in the upper walls or ceilings. The days were warm and the room stuffy.This kind of thing is an issue throughout Europe, of course, but after a while it gets pretty old for a traveling American. I did ask for and was cheerfully provided with an oscillating desk fan that made the room much more comfortable, though.
The other caveat: only one accessible electric outlet in the room, another between the bedroom and bathroom (and a shaver outlet next to the hair blower in the bathroom). I had to plug my fan into the passageway outlet and stand it on a chair facing my bed for the desired effect. The other outlet is by the night table on the right side of the bed (no outlet on the left). I could charge my phone or run my laptop but not both at once.