The shiping can get bad enough to make RA not worth while, but they still get my business much of the time. I've found that going through eBay and Amazon there's a high risk of getting counterfiet parts. Sure there are a lot of generic brand chinese production parts on both that are clearly such, but I've seen too many people buy name brands and get blatant counterfeit products there. I've seen "motorcraft" parts with motorcraft branding and lables on the boxes, but if you look at the fine print it is full of errors, misspellings, etc. Not suggesting that I won't buy Amazon and eBay parts, but if I feel that quality is critical, I'll buy RA because I'm more confident that the product is genuine.
Thing to watch for on RA is closeouts. I suspected that I needed wheel bearings on my little Kia. Doing the job on those you basically have to replace both the bearing and the hub, because you're going to damage it when pressing them apart and removing the inner from the hub. National Bearing for that are around $80 each from local parts store, the hub (Carquest/Dorman) is around $50. Between closeout price and coupon code I paid about $50/side before shiping. Turned out to be a good thing I saved the money. I screwed up pressing one side back together, wasn't pressing on the right spot and damaged the new bearing, then damaged the new hub taking it back apart. Back to RockAuto to order anothr set, still on closeout and still same price, about $60 delivered.
If I'd gone to the local auto parts store I'd be almost $400 into this job. Priced Amazon for the same brand parts might have saved me $50 over the local store prices. Right now (if I don't messit up again) I'm about $180 in with shipping.
What hurts is that after getting it apart, it was noticed that I probably didn't need bearings. Seems that I had a warped rotor. It's weird because the brakes were practically new and problem was persistant from before the brake job. That caused me to suspect a bad bearing or bent hub. I knew better than to buy the O'Reilly rotors when I got them, but it was quick and available. So throw in another $150 (RA again) to do another brake job, and $200 for a new pair of CV axles (one was slinging grease). The car has done 200k reliable miles so far, I'm shooting for atleast another 100k.