Personally, as a shopper my main goal is to find a great price. Service counts to, but price is key for me. If a place is *known* for bad or horrible service, I won't go there even if it's really cheap. But if service is pretty good, but someone has "terrific" service, and the pretty good service place has a much better price, then I'm with the pretty good service.
My money is very tight, and I just want to make sure I'm not going to get screwed over. If there is a $20 difference in an item, and the service differences are marginal, then I'm at the $20 cheaper place.
To me, service that pleases me is a seller who answers questions and sends tracking information quickly via e-mail, ships within a day or so, and makes things painless.