Who has the best customer service?

Where are you located, my best answer would be find a company that has RMA/repair centers closest to you. I personally have dealt with Asus, MSI and EVGA and have nothing but exceptional service.

I was going to get something from Sapphire until I read this:

"For any RMA claims against Sapphire, we have to send the card back and forth to Asia, and back to you afterwards, so there will be costs involved (Administration and Freight). Cost of each card is ranging from CAD$25-CAD$45 depending on your location/province (this does not include the transportation cost from you sending the defective card to us)."

I've also heard of hit and miss service from XFX, and Gigabyte, but I don't know about HIS.

I am going to share with you a story of the worst experience regarding for a gigabyte product.
I own a Gigabyte gtx 460 which I bought in 2010.
Second I am buying Gigabyte products for 14 years.
The case is that in the last September my gtx 460 had an issue with a horizontal green lines in the screen, and when I went to the local distrbutor in Egypt they refused to even check on the card, then I opened a ticket on Gigabyte website, the ticket was opened in the 9th of September and still going till date, why ? because they didn't respect their word and kept stalling all the way.
We agreed after lots of hassles that the product will be shipped outside of Egypt to the related service center in order to repair the card but only if it's repairable, I agreed with this but I wanted the local service in Egypt to check on it first to determine if it's repairable or not, and after I went there they examined it and sent the report to Gigabyte.
By the way I had an issue in 2012 with the windforce fan and the local distributor refused to even contact Gigabyte requesting for the spare part because the product was out of warranty, and when I opened a ticket online, Gigabyte sent the fan to the local distributor as a spare part, anyway here is the last reply from Gigabyte: "After viewing the video, our engineer concluded the issue is most likely caused by GPU damage. In this case, only *****(the related service center outside Egypt) has the facility to repair. However, as you are already aware that the product had already been out of warranty for over at least a year long, as a result, we no longer have any spare NVIDIA GeForce GTX 460 for repair"
After we had an agreement, and after I followed their instructions by doing that and go there and wait for contact...This is the end, they simply backed off and didn't respect their word, and they were bluffing and going in circles the whole time, they back stabbed me, and made me wait and given me hope from 9/9/2014 till their unfortunate reply in 1/5/2015.
I shared this just to warn you regarding their after purchase support, which is none, they will simply keep stall the while time without an end till you get bored and hate yourself because you trusted their products, I shared this to warn my fellow gamers from this inconsistent company that don't honor their responsibilities towards their supporters.
Gigabyte + Product = Warranty
I will share the tickets with you my dear readers so you can see Gigabyte true colors, you can copy and paste into you browser.
http://i.imgur.com/9onA1AY.png
http://i.imgur.com/zJI0l23.png
http://i.imgur.com/Ui1iK4h.png
http://i.imgur.com/dwGWhhb.png
http://i.imgur.com/3pqSpoD.png
http://i.imgur.com/ZOHQibD.png?1
http://i.imgur.com/oqT9nwc.png?1
http://i.imgur.com/ugX5uXj.png?1
http://i.imgur.com/53pjuyi.png?1
http://i.imgur.com/gR1ioID.png?1

One Piece of advice, do not hang a long time with your product especially if it's a gpu (whatever the brand), just enjoy it for while and then before the warranty ends just replace it with a new one.

You do get that your gtx 460 warranty was up so it wasn't gigabyte that was the issue it was you for wanting them to fix something that they weren't going to do for free. That's how all gpu companies work lol. I know this is old but i had to say it.