It looks like NBC is playing with social media to promote new programming. If you follow their Twitter account for the soon-to-air series, Grimm, they'll private message you with a code that allows you to preview the show's pilot.
When I'd seen the commercials for the show, it had piqued my interest. So, I hit their "follow" button Twitter. A short while later, I got notification of the private message's arrival. Donna and I sat down and watched the episode. It wasn't horrible. Has a decent enough premise. However, it was a bit on the predictable side.
I can't say that I'll go out of my way to watch the show, but I won't avoid it, either. If I happen to hit the channel when it's on, I might watch. If the actual series is better than the opener, then I might seek to watch it. Who knows, it could get good. Star Trenk: Next Generation started out poorly, then eventually found its stride. But, for now, it's a bit weak.