I spoke to John over at Costco, he is one of the people I know that works there. He said people return mattresses all the time, they can be taken back within reason, time wise, is what he said. Didn't give me any specific time frame. They have large plastic bags they give you when you return...
I had the PB278Q before getting my Qnix. I bought a refurb, it developed dead pixels after a few weeks, I also got headaches from the PWM dimming. I have had no such issues with my Qnix.
I can tell you one thing about those, they don't overclock, if you are looking to do that. They skip frames using a higher hz, just like every other multi input monitor.