EVGA uses the reference board from Nvidia. That means, EVGA is using the design by Nvidia without any changes. Just like Foxconn, XFX, and BGF. Other than Foxconn, I don't think anyone on the list even manufacture their own motherboards.
Asus and possibly Abit are the only 2 MB companies that doesn't use the Nvidia reference design that I'm aware of.
I have heard that EVGA does have excellent customer support when it comes to honoring their warranties. It seems they have been very liberal. Maybe because they are such a young company, they have to be.