People saying "if we lose this one, we aren't real contenders" need to get a grip. Every team in the league, including the eventual Super Bowl champion this year (assuming it isn't the 49ers, which I hope it isn't), would have a very difficult game on their hands at SF. I don't think there's a team in the league that could win more than six games if they played at SF 10 times. It's a huge game, and it would be a massive win, but it's hardly some crazy death blow if we lose, nor is it any statement on our team's ability to contend. You will find very few Super Bowl champions during the past decade that didn't take losses during the regular season in games like this one.
I see the game in a much more positive light; as something of a positive freeroll. If we win, then we take the lead over the Niners with a head-to-head win over them and the rest of our division games are home games. If we lose, then that sucks but it's not a hole we couldn't crawl out of.