I think it has more to do with matchups and teams than homefield.
In the case of the Eagles, the Eagles have ALWAYS been (this year I mean) an iffy home team at best, and while they have an explosive offense, their defense was really smoke and mirrors, and the Saints actually took a page out of Seattle's playbook by dominating the line of scrimmage with their D-Line and that was that for the Eagles. The Eagles were going nowhere. [Honestly I don't see a team as injured and flawed as the Saints going anywhere either but one of them had to win.]
As for Green Bay, San Fransisco on paper is a MUCH better team this year than Green Bay, and San Fran barely won today by the skin of their teeth. San Fran was supposed to win and it wasn't supposed to really be this close a game.
As for the Chiefs and the Colts, both are flawed teams with suspect defenses, and the Colts (the home team) did wind up winning. As for the Bengals, the Bengals played tight and made mistakes. This was the one really genuine upset IMHO where the better team simply didn't play a good game and their opponent did.
I expect the Panthers to beat San Fran possibly handily since the Panthers can go physically toe to toe with the Niners (and have proven it) are about as good a team, AND they are playing at home with a week's rest while the Niners will still be thawing out. As for New Orleans at Seattle, well we've seen that film before. Enough said. I also don't see New England losing in January in Foxborough to the Colts. If I had to predict an upset, I'd say that Denver *is* potentially vulnerable to the Chargers in Denver.
