I have used Sapphire in the past, but am very happy with XFX now (bought for the double lifetime warranty) which unfortunately, conked out a little over a month after I got it, well, one GPU did, anyhow. Fortunately, I chose XFX, and was pleasently surprised with their lack of questioning and fairly speedy RMA time (9 business days on cheapest to-them shipping option). My replacement is a champ. 😀
I have never had a Sapphire card give me a single issue. My previous 3 cards are all still alive and running well in friend's boxes. I just switched to XFX for the warranty.