Pros
The company has a strong presence in the Canadian market. Once the name Bank of Nova Scotia is on your resume it will at least get some attention. I was able to move to another financial services company because of the experience I gained with BNS. They also have decent pay intern-wise and a number of benefits such as discounted tickets, a relationship with Famous Players etc. I would strongly advise against taking a summer internship here unless it was in the Scene Program or Scotia Capital. Even in Scotia Capital do not expect to gain a vast array of knowledge.
Cons
The major problem is there is no streamlined recruiting procedure for summer students. Once you get in, you are on your own to ensure that you find a place to come back. Unlike other well defined intern programs there is simply no way to continue forward other then personal networking. However the roles that they have interns fill is typically pretty mundane. There is nothing but simple research and minimal analysis to be completed. There co-ops typically take up most of the intern spots at the firm with the "Scotia brats" taking up the rest. There are much better places to work.