This has been around since January of last year, and has been featured on sideline merchandise (not to mention all manner of merchandise), but so far as I know this is its first appearance on uniforms.
Picture to come.
UPDATE: Here's a good look:
Photo credit: Jim Biever, Packers.com
I don't mind this. I'm not a fan of all the clutter they slap on the back of the helmets, and at worst this is a little less busy than the red-white-and-blue logo they usually wear.
Kinda surprised they didn't do that with the league patch on the jerseys. Maybe they're saving that for the Super Bowl itself.