I think the difference with TNA and other new pins, is that it is made by a company and a person that are generally well liked, and that the game itself has generally positive reviews. It's not like a brand new Stern comes out and the Stern fanboys, or people newer to the hobby automatically give it a 10. Scott has brought the prototype to shows for the last year, and people have enjoyed playing his game even if they might not buy one for themselves. TNA had a different vibe about it, not just the machine itself, but the story behind it, and the people that worked to make it happen. I don't think you'll get people that will give it low ratings just to bring it down. But then again...this IS pinside.
I'm waiting to give my rating when I have the machine in-house and I can put plenty of single player games on it. I've been a fan since playing it at MGC last year, and I don't think that'll change once I have mine, but I just think it's fair to put a fair amount of play on a machine before giving it a rating, and not being one of those fanboys, which admittedly, I am.