I don't trust G.skill after reading one of their newegg responses. The guy purchased two 8GB (2x4GB) upgrade kits and they didn't work together in his PC. They would work individually but together the timings were out of whack. G.Skill's answer was "you purchased a 8GB upgrade kit, you should purchase a 16GB upgrade kit if you want to run 16GB of memory, that kit is only tested to work at 8GB" and they wouldn't help him.
Now I don't care how you slice it, that is horrible customer service and seeing as I wanted to do the exact same thing (4x4GB sticks) I chose to instead purchase a corsair kit.
Their CS is actually pretty good - they're one of the few companies that responds to Newegg reviews and issues a claim ticket then
. Realize that they aren't based in the US, so they generally don't understand your problem until you explain it to them directly (via the claim ticket they leave in their response). Their RAM is also lifetime warrantied.
I'm running two 2x4 kits right now with no issues. Problems can arise, especially if the guy A) bought 2 kits that didn't have the exact same timings and latencies, or B) one of the kits was faulty (i.e. timings were off or something along those lines). He could check their timings and RMA one of the kits if they didn't work.