First off... I am so glad this place managed to occupy that disgusting abandoned building on Bloor that existed for years. Such a prime location and I am glad they put in something useful like a book store rather than another sushi restaurant.
BMV is pretty massive. I would think you would have a hard time not finding what you are looking for at this place. They also have used DVDs (and laserdiscs) and I was over-the-moon when I found out they had used vinyl and CDs down in the basement! I try to keep crate digging spots a secret but the odds of finding something good in their vinyl collection is usually rare. It borderlines the selection at Goodwill, but I have found maybe a dozen records there in my time and most of them were under priced. They do work on a system where the older the record the more expensive it seems to be, so you might just want to stick to the late 70s early 80s selections for 3-4 dollars.
Staff has always been good, though one time around Christmas I had one of the most rude cashiers I've ever dealt with. It was as if I was inconveniencing him by buying from his store.