This is a great apartment and I highly recommend it! Its in a fantastic location, has a generous sized kitchen/living space, and the furnishings are lovely. I was travelling with a friend and the apartment was huge for just two guests, and the two bathrooms were fantastic.
I would say the apartment would be totally fine for three people. Four people might be a squeeze because one of the bedrooms isn't big (it has a double bed and is great for one person), but the two bathrooms and generous living/kitchen space means you could probably have four people stay.
In short, I highly recommend!