We have been to many museums that deal with the Holocaust, including the United States Holocaust Memorial Museum in Washington DC, and the Museum of Tolerance in Los Angeles.
Although Montreal's museum is not of the same grandiose scale as most of the others that we have seen, they did nothing short of an excellent job in packing in a lot of great information as well as personal stories. Their self-guided IPAD tour was very good, as were the exhibits and the videos within the museum itself.
We only allocated two hours at the museum due to other reviews, but personally I'd recommend leaving 3+ hours if you want to watch all the videos and really view and read the accompanying info from all the exhibits. We really enjoyed the museum, and were galad we made the jaunt from our hotel (which for us was a long metro ride from the old town).
SIDE NOTE:
If looking for a great Jewish deli nearby, go to Snowdon Deli