They have a lot of items at similar or slightly cheaper prices than other major pet stores like Pet Valu and PetSmart. They also had decent prices on a lot of dog grooming supplies like brushes and combs.
I really didn't appreciate the customer service here however, and looking at the Yelp reviews of other locations, it seems like a widespread issue. I enjoy going to my local PetValu (Bathurst&Centre) much better. The staff is so friendly and more willing to help you. At Ren's, no one comes up to you and the staff don't even acknowledge your pet, unlike most other pet stores. It wasn't really a friendly experience, which is what I expect from most pet stores.. so I wouldn't want to bring my pet here.
Another issue is that they offer price matching but it's a really pointless policy. They claim that the PetSmart website show prices in USD so they don't price match it. However, there is actually a different PetSmart site for the US and Canada. They also do not pricematch Amazon.ca even though the products are shipped and sold from Canada just because they do not have a "physical location". It's their loss since I would just buy the item cheaper on Amazon.ca and get it in 2 days with prime shipping.
I personally would just shop online next time ($60 minimum for free shipping). You can return items bought online in store as well I believe.