Playing with the shipping is one thing that gets me about rock auto. Usually I end up buying what I need locally because it ends up being cheaper. Plus their return game is a hassle. I bought body parts from them once, dodge truck frame mounts to be exact and they looked like someone made them in their backyard. They wanted me to send them back at my expense and the they'd decide if I'd get a refund or not. It wasn't worth doing that. Other times I've gotten things like fan belts that looked like they came out of an insurance claim and were older then the ones I was replacing. I've never bought parts like that from them since.
But when age or potential insurance damage won't affect the part and the shipping price game works on your favor it's the best online place to get decent priced parts from. Unless Amazon has it.