It's still a toss up to me. I really don't see the Seahawks scoring many points, because their offense just doesn't look that good. Even though Denver's defense isn't that great, their rush defense is one of the best in the league. If you can stop Seattle's running game, or even slow it down to a crawl, I don't think it'll be tough to beat them.
That said, Seattle's corners are so good that they'll be able to play a lot more man to man and bring a lot of pressure on Manning. Add that to the fact that it's going to be cold as all get out in that stadium, and it kind of favors the Seahawks.
Regardless, though, I'll still be rooting for (who I believe to be) the best quarterback in the game today and the Denver Broncos.