Simon's is one of those stores that's really cool for people who don't live in Quebec, but probably equally as lame for those who do.
Simons to me feels like H&M, but with a slightly better selection and far better fitting for people who aren't shaped like models. They have a great range of prices and brand names with something for almost everyone.
While I wouldn't say Simons is out of this world awesome, I think it's definitely worth a visit if you're in Montreal.