I spend my summers sitting in front of my computer at home, which means I spend lots of time on the internet looking at bike equipment deals -- and pestering vendors with questions like "can you match such and such a price?" or "will that take 28mm tires?"
Lots of vendors have real-time customer service -- chat windows and the like -- but rarely are they populated with knowledgeable help. I recall once asking backcountry.com, one of the online gear megastores, whether a particular telemark boot would work with my setup. The chat window response? "We can offer that at 10% off for you today." I learned from that exchange never to buy online without expressing some sort of concern first. So it's "good service" but not "helpful service."
Backcountry.com, by the way, now owns Competitive Cyclist. Competitive Cyclist has knowledgeable staff, but they can be jerks. I asked about warranty replacement on my Cervelo frame, which I bought there and recently cracked when (not) installing a headset. "Contact Cervelo," I was told, although I had bought the frame at CC and CC makes a big deal of covering its customers. (I gather CC is peeved to have lost that dealership, presumably when Cervelo stopped allowing any shipping of orders.)
Merlincycles does pretty well, considering the time zone differential. I usually get a response in 24-48 hours. But I'm peeved at Merlin. Why? Currently I am fighting a debt collector over a customs charge UPS tried to foist on me for a Merlin Cycles order.
Manufacturers are in the normal case dead last. I'm still waiting to hear from Hed about bearing replacement on an older wheel. Felt never responded to my question about the Z3. Too frequently I am told to "call the dealer."
One clear exception is John Neugent and his firm Neuvation -- now Neugent Cycling -- who can be very helpful, and is unfailingly gracious, by e-mail. Sam e-mailed for advice on brake pads before we left Portland on our eastern Sierras road trip in 2013. By Redding, California, we knew what to buy for our ride into the mountains west of Redding. Same with advice on squeak and bearing replacement for my C50 wheelset. On the other hand, John is a one-man customer service department and can get behind on his e-mails, and on a few occasions I've felt as if I offended him by asking for a discount. (To be fair, I was probably being a jerk. "How about <$3000 for a Red build on that sweet carbon rig?")
My surprising first choice for customer service? Pricepoint.com. Kevin Pak sends responses to my e-mails in hours, not days (yesterday it was minutes); the responses are topical; I even get follow-ups when I send my "thanks" e-mail ("No problem!" or the like); and all this from an enterprise that serves as the true bottom-price clearinghouse for industry overstock. And I'm unqualifiedly being a jerk in my requests to Pricepoint. "Can you go sub $2K for a Litespeed with Di2?" (Answer: not on the one I asked about, but the 2013 Ci2 is now $1999.)