We stayed twice at St Mary's recently. The rooms are small and the bathroom even smaller. The decor is minimal but for the price and location it is a bargain. One of the main metro lines is literally 20 meters away, it feels like a reasonably safe area and with Place De La Republique a short 2 mins walk you have access to restaurants, laundry, fast food outlets, Mobile phone companies etc.etc. The main complaint would be about the pillows which really leave to be desired...they are a long clumpy sausage wrapped in the bottom bed sheet and not long enough for both. The reception area and the people working there are really nice and the hotel is quite secure. We didn't try their breakfast as there are plenty of cafes around that although could be more expensive, offer a more enjoyable setting. Lobby computers were not working but wi-fi is free (although sometimes not reaching inside the room).
After staying there twice, if ever back in Paris soon, we might try another one in the same street or area as we did like the area a lot so won't stay with them again. It is very cheap and ok for 1-2 nights ...we spent longer there and coped ok.

Imagine a hotel that have different kinds of sheets in each bed, whith a different name of other hotels that isnt mary's? The rooms and the bathroom are really disgusting, don't believe the photos that you ser on their website! I stayed with 3 more people and along our 20 days trip we stayed in different hostels and this was by far the worst one. The rooms are very stuffy and the owner doesnt make any effort to try to understand you or help you. The breakfest is a joke, with dirty glasses, coffee from the machine and a very dirty room.
Don't recomend at all

The only pros of this hotel is near the metro station. Then, nth to be good to stay here. Rooms are crazily small and dusty. I even find some hair in the blanket. Even the weather is cold I don't put in on my bed. I'm wondering if the housekeeping did clean the room or not. The room and bed is a weird arrangement. room is so small but the bed is big (double bed). Crazy, how can I put my two luggages on floor. And the most thing exhausted me is when I leave the room, I found that some of my souvenirs are gone but I was in airport already. I guess it should be their action coz no one see my souvenir bag except they. Anyway, I strongly recommenned to NOT stay in this hotel. There are two more hotels just beside this one I'm sure either one if it much better than this.

We stayed in the 4 beds family suit at around 120euros per night, which relatively cheap for paris. The room was well equiped and well maintained. The only drawback was the poor internet signal on the forth floor where we were located. The bathroom could have been a bit cleaner, but all in all it wasn't horribly bad. The staff is very friendly, however I only communicated in french with most of them.
The location is very nice too. Located near Place de La République close to the Marais Area, it is within walking distance to at least three metro stations and many bus stops. The Seine is also approximately 15 minutes away on foot. The area is also packed with many bistrots, many brasseries and a lot of restaurants. In a way you get to experience the local Parisian life style to its fullest since the area is not very touristy.
In short it is a decent low budget hotel located in a great area.