M507 update.... Watching TV in bed this morning, the screen flashed and then black and sound cut out. The sound tried to come back a few times with a mild gray millisecond flash. At first I thought it was cable or Tivo-box, but turned out to be the TV. Powercycled, etc... nothing. Unfortunately, I'm outside the 90-day window for Costco to handle directly, but their Concierge rep took all of my info & had me do a power-cycle... then called Vizio on my behalf and conferenced me after providing all of my info.
Vizio is sending a 're-certified' replacement unit in 5-7 days, and used the box to ship my original TV back. I needed to provide my credit card info to opt for this expedited method, rather than waiting for a box, shipping mine back.. with Vizio sending a replacement only after the return is logged.
Hopefully the 're-certified' is just a refused delivery, rather than something sent back with screen issues. Not thrilled about the unit going bust, but Costco does take the pain out of contacting MFG for warranty support. Fingers crossed it all goes smoothly.