I've been buying from MEC since they were in a tiny one room space on 11 ave SW above a racket store. I've seen their gear go from underpriced, to vastly overpriced, and back to reasonable. The location on 10ave SW is great, it's huge and has pretty much everything you'd need for lightweight camping, cycling, boating, climbing etc.
They seem to have gotten their warehousing issues sorted out and will generally have the sizes I need for clothing. In some areas they don't have a very deep selection so if you want a choice of brands you'll most likely have to go somewhere else. Having said that their backpack department is insanely overdone. They'll have 20 kinds of backpacks that are the same size and function.
Like most retail places in Canada the staff seem to avoid talking to you or making eye contact and there is never enough people in the shoe department if there is anyone at all.
For some reason they made their parking lot a pay lot. I've never paid and never will but it still astounds me that they'd do that.
All told, you'll get low service with average prices but chances are you'll find what you need and a few things you didn't know you need.