It is definitely location by location basis. Some are awesome and some(most) are awful.
In my experience its mostly been the customer service. I'm a manager and sell guitars for a living, not that that has much to do with animals, but its still about finding the exact right things for the right person through conversation and knowledge, and being able to answer questions. You represent the products you're selling, you should be the go-to for them, and as someone said before..if they don't know, they should be referring you to someone who does.
Every time I've gone in, since I'm a new owner I have a lot of questions. I always start out with someone nearby and ask "Is there someone here I can ask questions to about bearded dragons?"
They always refer me to someone else, sometimes more than once..which as a customer that tends to aggravate me.
Finally when the brave soul stays and I ask a question, they just start reading the back of products with me, like I can't do that myself. Usually I just say "Nevermind" and take the items back, and do research on my phone while they just silently slip away..haha :lol:
Every now and then though someone will come up and ask if I need help which is always nice, and when I do..once in a great while you'll get someone extremely knowledgeable who will talk to you for days about the different bulbs, brands, foods, etc.
At this point I don't mind as much, I've come to know whats what and what I need through you guys here and other research, but its pretty disappointing most people there don't seem to know a thing about their own products, and even worse, about their own animals their selling with probably an extreme lack of useful information. Starting out with a brand new pet, you'd hope the people there who take care of them know a thing or two more than you do.
Then again, my last experience at Petco was being referred to an employee who owns 4 beardies. Now that's the help people need, and because there is personal experience, you couldn't ask for better help when you need it from someone more experienced than you. This is all obviously store by store basis though, but generally in my experience the people working there seem pretty unknowledgeable when it comes to anything besides fish.