I like quality products, plenty of choice and reasonable shipping. It's great if you can set up a search engine that actually works, and will pull up, for example, all "green prints" when I want them. All too often I'll try to do something like that and all I get is "no products found". Really? A whole site without a single green -- or blue -- print? No, that's a lousy search engine, and it means I have to waste a lot of time going through the entire site, so I don't bother. I do buy a lot from the Connecting Threads site because it's fun to look at and well organized. I really like the fact that if you buy $50 worth of fabric, the shipping is free. I'll often make sure I buy that much in order to get the free shipping. They have low to reasonable prices and great fabrics. Why can't other sites do it?
If it's a new site, I'll buy a very small amount just to see what kind of quality and customer service I get. I once spent quite a bit at a site, based on excellent reputation, and the fabric was horrible. So horrible I now use it for practice only, and it wasn't cheap! But customer service was nasty, and there was no way they'd let me return it. You can be sure I'll never buy from them again. The kicker here is that if I mentioned the name, everyone on this thread would recognize it!
I keep going back to sites that supply quality fabrics for reasonable prices, and who treat me like a customer should be treated. I'm a nice person. I will bend over backwards to help make something right. I am 100% kind to the person in customer service, no matter how badly they treat me. I've never lost my temper on the phone. I just don't use the site again if customer service gets nasty with me. (Oh, you'd be surprised!) Customer service is your front line, the "face" of your site. If they can't be nice to customers, regardless of circumstances, then you will lose customers, full stop. That doesn't mean they have to "cave in" every time a customer makes a demand. I have no problem accepting the boundaries of a transaction, what they legally can and cannot do for a given transaction, as long as they are explained clearly and kindly to me. No problem, and I think that would be true for most anyone, unless they have a chip on their shoulder. But don't sell me $11/yard fabric that is so thin is practically transparent, and then refuse to take it back!
Oh, and I shop on line because I only have one decent Quilt Shop available to me, and while it's very nice, it doesn't carry everything. So my on line purchases supplement that.
One thing I would LOVE to see in an on line store is coordinated fabrics, so that when I'm putting a quilt together, I have all of the coordinating fabrics in one place, and I don't have to go from shop to shop, and just hope the colors will coordinate. So carrying a line of coordinating fabrics would score high on my list.
And finally, having a design board, where I can put fabrics and look at them next to each other, is high on my priority list. Even if the colors don't ring true on my screen, and I don't have a lot of problem with that because I have the latest Mac, and they are fabulous for colors, but you never know under what conditions the photos were taken -- the wrong light can throw colors off. But being able to put the fabrics next to each other helps to make up for those kinds of problems.
Hope this helps.