After a long search on the web for a hotel in Stockholm that wasn't a hostel, wasn't expensive, had a private bathroom and wasn't to far from the city center we decided to book a four night stay at Loginns hotel.
We were both very happy about the fact the hotel was on boat but were worried about the bad comments that we had read on various web sites.
The trip started off badly as we missed our flight and therefore arrived a day late only to find our room was no longer available.
The owner was very nice and arranged a room in a near by boat as there were no rooms left in his hotel for that night.
The following day we were invited for breakfast at Loginns and then given a nice room on the first floor with a bathroom.(shower,wash basins and toliet) the room was small but clean and had a beautiful view of the city hall.
Most of the day we were visiting the city so we were in the hotel just for the buffet breakfast which was served in the restaurant upstairs, and in the evening to go to sleep.
We enjoyed our stay and the staff were very nice.If we return to Stockholm we would be very very happy to return to Loginns.
p.s the hotel is just a short walk from three metro stations, the nearest is Mariatorget but Slussen and Gamlastan are not that far away if you would like to walk by the harbour.

The Loginn hotel was a great choice for us as we were on a very tight budget, the triple room we got was much cheaper than any of the other hostels or hotels that were available when we booked. The general consensus of reviews I read was that you get what you pay for and I agree completely. The "triple" room we had was miniscule and had a very small closet in the next room with a (comically loud) toilet, sink and shower area... One thing that was good about the room was the view we got from our porthole, we had a direct view to the other side of the water where the beautiful town hall stands.

The staff were mostly friendly and generally helpful and the boat is just a few minutes walk away from either Gamla Stan metro or Skanskull metro if you know the short cuts.
We were also offered a simple but lovely breakfast and free juice from a machine that runs all day in the bar upstairs.

Overall, I had a great stay and would definitely recommend this hotel for those on a budget, as Stockholm itself is far from cheap.

In the discription of LogInn Hostels.com site, it was clearly written that breakfast was included to the stay, and it was the reason why we chose this hostel, but to our big dissapointment it was not and the staff wasn't as sorry as I would expect them to be in this kind of situation. The hostel blaimed the website we had used(hostels.com), that they haven't changed this information, even though the breakfast hasn't been included for over a year.

bad sides: the hostel it's situated 15 minutes walk from Slussen subway-station, it felt a bit far away when it was really cold and windy during our stay. Then, I had booked a doublebed-room for us, but for some reason we got a strainge combination of doublebed and bunkbed with 120cm wide double and over it, a regular 80 cm bed. the garderobe didnt have any hooks inside and all in all the room could have needed a little renovation. walking to old town goes well.

good sides: The bathrooms were nice and clean, but if you are really tall, you can't stand straight. the view from the room to the city hall is like in the pictures. sleeping in a ship is an experience.

summary: the hostel was cheap, so I guess you get what you pay for, but there are plenty of boathostels to choose from in Stockholm.

If you are looking to stay in Stockholm on the cheap and aren't a germophobe this is a good option. If you are solo traveling just go to a hostel, but two people traveling together get a better price here. The hotel is dated and somewhat grubby, and they definitely don't clean your room or change linens every day. The rooms are really tiny, and the bathrooms are too, with grungy tile grout. Not a place to be spending many waking hours in (but really, who spends that much time in their hotel other than for sleeping anyway). We were there in winter, and the room was quite warm, not a whole lot of ventilation. The bed was comfortable.
Staff are friendly enough, but not a whole lot of attention to detail. The breakfast (70kr) was pretty basic, but good. From the restaurant you get a great sunrise view across the water to Norrmalm and a bit of Gamla Stan.
The best thing about this place is its location. It's just a short walk from both Gamla Stan and the center of Sodermalm. About a 5 minute (100kr) taxi ride from Stockholm's centralstation, where the arlanda express from the airport arrives. It was also kind of cool to be on a boat. One night it was very windy, and you could feel the boat rock a tiny bit from side to side. That was interesting. It was a bit noisy at night, but we had the room right next to the entrance. Any other room would probably have been quieter.
One thing I saw in another review before we went there was a complaint about there being no internet. Maybe that was the case at the time but they do have free wifi now.