I think the 'boys are going to be a lot better this year with an improved secondary. I wouldn't take too much away from the opening game, though, especially against a depleted Giants secondary.
Remember there were several dropped passes, a non-called defensive holding that probably saved a TD, generally just lots of first-game-of-the-season mistakes that hurt the Giants more than the Cowboys. That's football; it doesn't take away from the fact that the Cowboys won fair and square, and they look a lot better than they have in the last couple of years. Still, they were hardly what I would call dominant.
In the end we'll just have to see... the Super Bowl formula lately has been to make the playoffs and get healthy and hot at the end of the season.