The Petsmarts around here seem to be fairly nice. They have some fish in stock that I wouldn't expect from them...Angelicus and Yoyo botias, nice lookin baby sailfin plecos (the real ones, gibbeceps), and a few here and there that are outside the norm. Tanks are all clean and healthy, and most importantly, no dead fish floating around. Also, their prices for what interesting fish they do have are on average a buck or more cheaper than more specialized fish stores.
I would not choose them by any means over my LFS on a regular basis though simply because I much more value their expertise and ability to get what I want in a reasonable time, but all in all, I think Petsmart takes their tropical fish department more seriously than any Walmart or Kmart would for sure.
Another thing that I am not able to do at a Petsmart is catch and bag my own fish. I always like to do this so I can get the exact fish I want and not cause them too much duress whilst doing so, but I cringe sometimes when I see some of the people trying to catch a fish for me. Having LFS work experience in my background certainly helps my cause when it comes to asking to net my own fish, and when I have asked to do that at Petsmart, they have told me a flat out 'NO!' even after talking with them about my history. So all in all, you get some benefit at a Petsmart in that they have decent fish at good prices, but you definately lose something in the fact that they have not much extra experience when it comes to things and aren't necessessarily the most skilled at catching the fish that you want.
One of my biggest pet peaves is when an employee doesn't even try to get you the fish you want when you are directing them to the fish. All fish are not created equal!