People on this site knock petsmart and petco alot.. But I for one am a fan of Petsmart at least(been too long since I've been in a Petco, so no opinion there) and here's why:

1) Unlike all other "Generic pet stores", they don't sell cats and dogs. Cats and dogs sold in the generic pet stores are always mistreated, purchased from irresponsible breeders, and kept in dirty tiny cages. The dogs are never walked, the cats are never played with.. it's just horrible. Petsmart on the other hand has adoption centers where on the weekends or something local rescue centers bring in cats and dogs that need to go to caring homes. I don't think Petsmart makes any money off an animal being adopted. Of course I'm sure they don't do it 100% for charity, they probably expect new pet owners to use their in-store groomers and purchase food/supplies there. But still, they don't support the "pet store dog/cat sales".

2) I've had great luck with fish bought there. I'm sure that it differs from store to store and probably has more to do with the employees working at the one near here, but I have to say that at least that one has clean tanks with healthy fish that have stayed healthy after being purchased and brought home.

3) You can find one near most large cities in the US pretty much.. So you always have something to fall back on if needed.

4) I saw a Petsmart employee one time refuse to sell a chameleon to someone who didn't know what the hell they were doing and had no cage or anything to keep the chameleon in other than one of those little plastic critter cages.

5) Most of their inventory and sales are pet supplies, not pets. This is a good thing in my opinion, it means they're not relying on impulse purchases for their profits.

The pet stores I absolutely refuse to shop at, unless there is no other way to feed a pet, are those smallish ones you find in malls and such that have the wall of dogs/cats in tiny overcrowded cages behind the large glass window. Terrible care of the animals they have, and they rely entirely on impulse purchases for the majority of their income.