Location, location, location! This was a unique experience for our family. The boat is located right near the Place de la Concorde, which places it within walking distance to the Louvre, Eiffel Tower, Musee D'Orsay, Notre Dame, the Grand Palais, Opera, and Les Invalides to name a few top sites. Marc and Diana were great hosts, and were very responsive. Check-in was easy (once your taxi finds the place!) and the boat is cozy and inviting. Traffic noise wasn't awful, being located right below a major thoroughfare, but be prepared to hear vehicles and sirens on the early AM side.
The boat itself is almost a hundred years old, so it shows a little wear. You can't expect a hotel experience, but if you are adventurous, you'll have a great stay. The kitchen is well appointed, and we were able to make a few meals with the ingredients we purchased at local markets. There is a shower with scorching hot water which was nice :) Wifi on the boat saved our data roaming expenses, too. It is, however, tight quarters. 5 guests is a bit of a stretch, as one person will end up on a futon mattress on the floor. Water traffic during the day and evening keeps the boat in gentle motion, but our two motion sickness prone members didn't have any problems. There is little to no water traffic after 10 or 11, so sleeping is very still.
It was fairly chilly during our stay, but the boat was nice and toasty. One complaint is that it is oil heated, and there is a pervasive smell of heating oil. There are plenty of windows to air it out, and it may not be an issue during the warmer months, but that was the only unpleasant issue.
Overall, our stay was great. I was traveling for business, so I wasn't with my family every night, but Marc and Diana made them feel very safe and secure.