My fiance and I stayed at the Chatueau Champlain last year. The hotel itself is very nice with an ornate lobby. Nothing spectacular about the rooms. The concierge lounge was a bit awkwardly shaped and crowded (it was the last week of August so lots of kids and parents), but the service and food were good.

In terms of location, it's a bit on the outskirts of the city. But there is a park and lots of restaurants within a 10 minute walk, including a couple of fancy ones. Also, you can get to the subway from the lobby which is nice.

Hopefully this doesn't happen to you, but when we went hotel union workers were picketing in the lobby.

Best of luck. Montreal is such a beautiful and fun city. We loved it.