They're so large now that there's BOUND to some unhappy customers. I've personally ordered over $15,000 worth of merchandise from them over the past 3-4 years, and I haven't had one single problem yet. They've always been kind and responsive on the phone/email, and they are still the fastest shipping store I regularly purchase from.
They may not have the absolute lowest price on every item, but I don't think twice about buying everything I need there, I don't mind paying alittle extra for piece of mind and quick shipping.
In short, no they aren't "going down hill".