I have bought some things at this store in Oshawa, but I haven't taken any courses through them. I have heard from a couple people who did take the course that they were very professional. They were always helpful and knowledgeable when I went into the store.
I have taken a variety of courses through Dive Source in Oshawa, which was mentioned above, and I can therefore vouch for them. I completed my open water diver certification, as well as my emergency first responders course through them. I am planning to take further courses such as advanced open water diver and others through them.
Edit to add -----
A month ago or so one of the dive masters actually put together an event called 'Dive for the troops', unfortunately I was not able to get the night off work.