We stayed here in November 2012 and got the one bed suite which also has a sofa bed in the living area. We were two adults, a 3 year old and a 1 year old.
I booked over the phone which was very efficient and smooth. No special offers or discounts but the room rate was reasonable for the size of room and hotel.
We arrived before check in time but they told us that our room was ready and we went up (which is great when traveling with kids!). The hotel lobby is very nice and smells so good, I think they have special candles.

Room:
Really great size, a winner for families. Even with the sofa bed 'made up' and a pack and play in the room there was ample room for the kids to run around.
Kitchenette is fairly well stocked - microwave, fridge, toaster etc. Also the nespresso coffee machine that everyone else mentions. You get 3 nespresso capsules a day btw or they charge you for more.
Bathroom was large and had a huge bath and separate shower which was nice. Double sink.
The only *small* negative with the room is that the actual bedroom is an internal room which is why the have partial glass doors so that some natural light comes through. However, our point for having a one bed suite was so that we could put the kids to bed and then stay up in our room with lights on/tv etc but the light obviously travels through the glass door. Minor point. Our kids slept so it wasn't really a huge issue.
Our room was at the back of the hotel and far from the elevators, was practically silent. Maybe it is different in summer time but I didn't think the location was noisy overall and the street side was even quiet in my opinion.

Location:
Great location for the old town and tourist type things. We also were able to walk to the downtown area within 10 minutes. If we wanted to go further the hotel would call a cab, e.g. we visited the biodome (well worth it with children) which was about 15 mins cab ride and $20.

Hotel Service:
Very good, not special, but good. Concierge was well informed and helpful. We needed to visit a Dr's while staying and he directed us to several clinics within walking distance.
The chamber maid service/room cleaning was actually very good to the point that I commented on it - they really cleaned the room properly every day and also provided 'turn down' with bottled water which is a nice touch.
Free wifi which I was happy about.

Other:
My husband and daughter used the swimming pool at the Intercontinental (I think!) which has a deal with the St Sulpice. You have to pay to use the facilities though so not really worth it unless you are going to spend a couple of hours there. Apparently the pool was ok, not huge and quite cold. Also a good 10-15 minutes walk so not exactly convenient.

There are loads of places to eat in the local area around the hotel and we found plenty of places that would do carry out. Very few places seem to deliver in Montreal.

I would recommend the hotel again based on the good old town location, on a very pretty street and the comfortable and clean, very large rooms. Good hotel and worth the price.