Like others, I've heard a ton of complaints about the place. So I was a bit wary my first time around, but the staff have been nothing but nice to me. We've even talked about the products on occasion a bit before I left.
I mostly go in to buy Manga and Gundam Models so I'll talk about those.
-Manga-
Their manga selection is very good. Much better than anything you'll find at a local Chapters or Indigo. I think that alone is worth it to make the trip worth it because the books are sold for the exact retail on the book. I've never really noticed a sale with the exception of Black Friday. But I really can't complain about prices. Probably best place in Toronto to just go down and pick up a book.
-Gunpla-
If you're interested in Gundams/Gunpla they have a huge selection. It's just a ginormous wall in the back. It's huge and well organized by number and series. It could use maybe a bit of signage to tell you where the different series are if it's your first time in because it's so big but past that I've never had a problem with it. You're going to typically be paying two times the price from Japan. This is mostly to cover import fees plus the bonus on top that makes it worth it for them. Like almost any gunpla hobbyist will tell you in NA. You're probably better ordering online somewhere, but to be able to go down and just pick up a model anytime I want makes it more than worth saving a bit and waiting forever.
Also worth mentioning is their website: http://animextreme.ca/
It's very well put together and even details whether an item is sold out or not. Sadly it does not detail every item they have in stock such as manga, which would be a plus. Worth it for figures and models though.
In conclusion, I can see why some people may be wary. But ultimately, this is the best place in Toronto for this sort of thing.