Montreal has a great mix of hotel choices. I recommend:
Le St- Martin Hotel Particulier: I stayed downtown in this fairly new boutique hotel at 980 Boulevard De Maisonneuve West. The rooms were excellent and I thought the location was very good for exploring all areas of the city. It is across the street from a Metro stop and there is a cab stand across the street. You can walk pretty much everywhere from there. I found the hotel through Jetsetter.com.
I also checked out the Le Petit Hotel in Vieux Montreal at 168 Saint-Paul St. West. It is an small boutique hotel with a sleek contemporary vibe.
I did stop in at the new Zero1 Hotel at 01 Boul. Rene Levesque Est. It is very sleek and contemporary in its design. The immediate area is north of the Old Town and China Town, East of Downtown and South of The Plateau and the Quartier Latin. It has been getting good press and reviews. It is in a a good location, particularly if you want to be at some of the festivals and need to be a short walk to The Place de Artes and the Quartier des Spectacles, which is a few blocks away.
Another option is The Hotel Relais de Lyonnais at 1595 Rue Saint-Denis in the Quartier Latin (Latin Quarter). A small boutique hotel, it has four suites and three regular rooms along the front of the hotel. Supposedly the noise can be an issue along the front in the regular rooms, due to the cafes and bars in the neighborhood, so ask for a quiet room in the back. I would definitely consider staying here in the future. It was well located to many of the areas that I enjoyed exploring and several of the restaurants I recommend. They own a small cafe below the hotel, La Brioche Lyonnaise, where breakfast is served.
I thought the St. Paul Hotel, at 355 Rue McGill, looked good as did Hotel Nelligan in Vieux Montreal. The owner at the Cluny Art Bar and their other restaurant, Titanic, in Vieux Montreal likes the Hotel Gault and said it was his favorite in town.
The new ALT Hotel in Griffintown has received some great press also.