Let me bring it all together one more time before Favre joins the Vikings.
The Vikings should not sign Brett Favre.
Favre turns 40 years old this season. He throws a lot of interceptions (20+ in three of the past six seasons, leading the league in two of the past four seasons). He hasn't had a meaningful playoff run in a dozen years, and Favre's lasting playoff images of the '00s are interceptions and home losses. Experience hasn't lowered his interception rate or made him reliable in the playoffs.
The Vikings, like the Packers and Bears, have an easy schedule in 2009. Each of these teams gets four games against the NFC West, a home-and-home with the Lions, and the Bengals and Browns: each of these teams should go at least 6-2 against that slate (and if one of these teams goes 8-0 against this slate, then just splits the home-and-homes with the other division games, that team wins at least 10 games). The Vikes have a good shot of winning at least 11 games in 2009, regardless of who is at quarterback. In fact, if they are any sort of good team at all they should go at least 9-7, regardless of quarterback.
It just doesn't make sense to me. Sage Ronsenfels' biggest demerits are lack of playing time and like Favre, turnovers. But he's 31 years old, and in the last two seasons completed 64.2% and 66.7 % of his passes. He's certainly an upgrade over Gus Frerotte, who went 8-3 with this Viking team in 2008 despite throwing a bunch of interceptions and generally sucking.
Certainly Brett Favre could lead the Vikings to an 11-5 season or better in 2009. But so could Sage Rosenfels! And since, as I believe, Favre is not a reliable playoff quarterback, I don't see any reason for the Vikings to sign him (except to boost ticket sales, and since the Vikings do risk blackouts, especially if they struggle early, that may be a significant factor). Perhaps he gives the Vikes a slightly better chance in 2009, but then he probably retires, and then what? The Vikes spend 2010 finding out if Rosenfels is good enough instead of 2009? I'd rather find out about Rosenfels now. He might be a good enough quarterback to make a team with a great running game and a great defense a contender over the next few seasons. He might--I don't know. But I don't really think he makes the 2009 Vikings significantly worse than Brett Favre would.
Stay away, Vikings. Set a deadline of yesterday, and move on.