I would not approach multiculturalism as a phenomenon with advantages and disadvantages. It is a complex aspect of societies in Canadian cities (rural Canada tends to be "less" multicultural, although that is not entirely true). Multiculturalism as official policy is contrived, partly because multiculturalism is defined from a perspective of a society that is deemed to be essentially Anglo-French, which is supposed to be accepting of people of different geographical and historical origins, religions, and nationalities (among other factors). The reality of multiculturalism is that it is still more difficult for people of visible minorities and peoples from the First Nations to have access to the same quality of life, jobs, political life, and housing when compared to the opportunities that "mainstream" people have in Canada. Multiculturalism is a fixed (non-dynamic) label for a society comprised of a heterogeneous population that is in constant flux and which is difficult to define at any given point in time.
These are quite general, and offer some brief ideas
Brings in new ideas and opens up the world
Larger variety of reastaurants with different foods
Opportunity to learn about other cultures and countries, and try their nice food :)
Grow as a person as you meet different people with different views, and learn to respect others and be open-minded.
Less boring with a nice mix of people
To be honest, Canada's population is ultimately multicultural, in the sense that most Canadians have European ancestry and are not in fact native Americans, when cut comes to chase.
Learn to be tolerant of others
See world from other perspectives and points of view
Growing up in a multicultural society helps erase negative stereotypes, because ppl come to the realisation that ppl are different within the same culture. So there are some bad ppl from one's own culture, and another's, but there are also some really good ppl in one's own culture and anothers.
Sometimes some groups can form their own groups and become isolated from society
Sometimes and unfortunately, racism occurs