So far, so good. I have done quite a bit of mental juggling sorting through stuff available to build systems. You have to inspect and know what hardware goes together well. I have seen "errors" such as misplaced price tags and such. I found an Intel Boxed Quad Core/Fan kit sealed in the box with heat sink compound goo as if it had been pre-tested, but it passed all tests, so I don't know what that was about.
I have had problems with BestBuy in the past, and I won't touch anything reboxed from them. Fortunately I have taken open box equipment to their bench to try before buying and all failed before I lost any money. I bought memory recently without incident.
Everywhere seems to have a turnover of kids. Never make an assumption that anyone you buy from knows enough or cares enough to look out for you.