We (4 adults, 1 teen) loved our stay in Colmar! The place is spacious and beautifully decorated. We were very comfortable and felt at home. The location is fantastic! Close to everything we wanted, Unterlinden Museum, restaurants, shops, culture, architecture, etc.
The trade-off to the location is that you are right in the middle of the nightlife. And Colmar is a party town. We happened to be there for the national Musical Celebration, so it was probably more 'rocking' than usual. This June was hotter than usual and we had to leave the windows open at night. It was definitely noisy, but the noise didn't bother us much. Any other time of year would have been no issue at all.
Colmar is a great base for travel in the region. We highly recommend Sebastien's place.