Hardware France publish 6 monthly return rates from one of Europes biggest etailers (see other editions on the site to get a 3-4 year overview) The minimum sample size is fairly large. It makes some sobering reading for those AMD cheerleaders taking potshots at EVGA.
http://www.hardware.fr/articles/934-5/cartes-graphiques.html
Bear in mind that these are total returns. Failures, buyers remorse, and customer dissatisfaction ( coil whine, too high expectation etc.) are all included.
my personal experience with EVGA has been exemplary. 8800U (3), GTX 280 (2), GTX 580, GTX 780 - all overclocked, no complaints.